GB2251697A

GB2251697A - Shaft having torque indication means

Info

Publication number: GB2251697A
Application number: GB9200626A
Authority: GB
Inventors: Ernst-Bernhard Arand; Hartmut Zoppke
Original assignee: GKN Cardantec International GmbH
Current assignee: GKN Driveline International GmbH
Priority date: 1991-01-14
Filing date: 1992-01-13
Publication date: 1992-07-15
Anticipated expiration: 2012-01-13
Also published as: ITMI920036A1; FR2671591B1; GB9200626D0; SE9200045D0; IT1263172B; GB2251697B; SE9200045L; DE4100830C1; FR2671591A1; ITMI920036A0

Abstract

A shaft for torque transmission, e.g. a propeller shaft for a motor vehicle, includes a holding element 32 which extends co-axially relative to the shaft and has one end non-rotatingly connected thereto, the other end of the holding element and the adjacent part of the shaft having cooperating indicating means for indicating shaft twisting under torque, the indicating means comprising capsules 23, 24 of a marking material eg, a dye, and a member 21 arranged to break the capsules on excessive twisting of the shaft. <IMAGE>

Description

Title: Shaft having torque indicating means Description of Invention This invention relates to a shaft for torque transmission, including a holding element which extends co-axially relative to the shaft and is not subject to torque, one end of the holding element being non-rotatingly connected to the shaft and the other end of the holding element, and the shaft adjacent such other end, being provided with cooperating elements of indicating means for indicating deformation of the shaft caused by torque. The shaft may be a length-adjustable propeller shaft for the driveline of a motor vehicle.

Such a shaft, e.g. a length-adjustable propeller shaft as disclosed in DE3636167C, provides for torque transmission between driveline components which it connects. Such propeller shafts are safety-critical components especially in the case of commercial vehicles which incorporate engine or transmission brakes, because they have to transmit braking forces to the wheels of the vehicle.

Hence it is desirable to provide such a propeller shaft with means for indicating if the shaft has been subject to any overloading, and the propeller shaft disclosed by the prior art above referred to includes indicating means for showing if any plastic deformation of the shaft has been caused by overloading. However, overloading may also occur in a range which causes elastic deformation of the shaft only, which cannot be detected by the prior art indicating device.

It is the object of the present invention to provide means for indicating any torque overload which may occur in a shaft as first referred to herein, whether such overload causes elastic or plastic deformation of the shaft.

According to the present invention, the cooperating elements of the indicating means, associated with the holding element on the one hand and the shaft on the other hand, comprise at least one member containing a marking material and a member arranged to engage said at least one member upon shaft overload to cause release of said marking material.

This measure, according to the invention, permits a permanent indication of excess twisting having taking place in the shaft, independently of whether such deformation is elastic or plastic. Twisting caused by overloading results in release of the marking material which is readily visually identifiable.

Preferably the marking material comprises a dye, contained in a readily destructible, e.g. frangible, capsule arranged to be engaged by a pin which moves relative thereto as the shaft twists, and there are two such capsules spaced circumferentially of the shaft on opposite sides of the pin, with a space therebetween providing for relative movement of the pin and capsules for twisting of the shaft corresponding to tolerable loadings thereof.

The dye capsules may be held in axially extending, radially inwardly facing recesses of the holding element which extends co-axially on the exterior of the shaft, the pin being associated with the shaft part disposed radially inwardly of the holding element and extending radially outwardly into the region of the dye capsules.

For achieving uniform distribution of the dye when a capsule thereof is fractured, it is proposed that the dye capsules, on their radially outermost parts, should be covered by an absorbent material. It is advantageous if such absorbent material is covered by a window of a transparent material, e.g. a transparent plastics material such as "Plexiglass"

Preferably, when the shaft is not subject to any torque, there is a space between the pin and each of the capsules on opposite sides thereof in the circurnferential direction of the shaft, to provide the region of shaft deflection corresponding to acceptable torque in the shaft.

To ensure that, under excess torque, the dye is released without fail, the capsules thereof preferably are of a brittle material, e.g. glass. The dye is preferably a red liquid, and it has been found to be advantageous for the dye capsules to be in contact with each other by way of the absorbent material.

Different arrangements are possible for the holding element. For example, it may take the form of a cover tube embracing the shaft along at least parts of its length, or it may be an indicating shaft disposed within the torquetransmitting shaft which is of hollow configuration.

If the holding element takes the form of a cover tube, two different arrangements are proposed in the case of a torque-transmitting shaft which comprises two parts connected to one another by length-adjusting means to provide for changes in the overall length of the shaft. In a first variant, the cover tube is connected to one shaft part and, extending over the length adjusting means of the shaft, is guided as far as the region of the free end of the other shaft part.

The indicating means are provided at such free end of the other shaft and the adjacent end of the cover tube.

With such an arrangement, the position of the free end of the cover tube relative to the adjacent shaft part changes as the shaft length changes. In this case, it is proposed to arrange the shape and/or disposition of the dye capsules to correspond to the axial movement of the elements of the indicating means relative to one another. This makes it possible to adapt the tolerance region to permissible torsional deflection in the shaft as its length changes.

Under a given torque, shaft deformation is greater when it is extended to its longest length than when the shaft is contracted to its shortest length, so when the shaft is extended a higher deflection thereof may still be within the permissible range.

Alternatively, one end of the cover tube may be secured to one shaft part in the region of the length adjusting means of the shaft, the other end of the cover tube and the adjacent region of the same shaft part carrying the elements of the indicating means. In this case, the elements of the indicating means do not move axially relative to one another as the shaft length changes.

The elements of the indicating means are preferably disposed in a radial space defined between the cover tube and adjacent shaft part, in which case it is possible to exchange the positions of the elements of the indicating means.

The length of the dye capsules may correspond to the change in shaft length provided by the length adjusting means thereof.

If the holding element comprises an indicating shaft disposed within the torque-transmitting shaft, such indicating shaft may be non-rotatingly connected to one shaft part at the greatest possible distance from its free end at which one element of the indicating means is carried. The indicating means may be disposed in an axially facing aperture at the free end of the shaft part, preferably in a central aperture of a universal joint yoke in a propeller shaft.

If the indicating shaft extends through the centre of two shaft parts which are axially movable relative to one another, it is proposed that the indicating shaft should be guided so as to be axially movable relative to the shaft part to which it is non-rotatingly connected. Alternatively, the indicating shaft may be axially movable relative to the element of the indicating means with which it is associated.

The element of the indicating means associated with the indicating shaft may extend radially outwardly from the indicating shaft and be guided in an aperture in the adjacent part of the torque-transmitting shaft, the aperture guiding the element of the indicating means for circumferential movement only so that the indicating shaft is fixed axially relative to the indicating means. Disposing the cooperating elements of the indicating means as far as possible towards the outer circumference of a shaft part or component connected thereto results in larger relative movements taking place between the cooperating elements of the indicating means for a given twist in the torque-transmitting shaft.

Preferably the indicating shaft, between its connection to a shaft part and the indicating means, is supported and guided by at least one supporting element. It is advantageous for the indicating shaft to be securely supported at high rotational speeds of the shaft.

One of the elements of the indicating means may form part of or be disposed in the region of a window provided in a shaft part or cover tube. Such window may be closed by a piece of transparent or translucent material, e.g. a plastics material such as "Plexiglass"

The invention will now be described by way of example with reference to the accompanying drawings, of which:: Figure 1 is an elevation, partly in section, of a length-adjustable propeller shaft according to the invention; Figure 2 is a view as Figure 1 of a further embodiment of propeller shaft according to the invention; Figure 3 is a longitudinal section through an indicating means which may be provided in the detail "Z" of Figure 1 or Figure 2; Figure 4 is a transverse section through the indicating means of Figure 3; Figure 5 is an elevation, partly sectioned, of a further embodiment of length-adjustable propeller shaft according to the invention; Figure 6 is a view as Figure 5 of yet a further embodiment of propeller shaft according to the invention; Figure 7a is a section on the line C-D of Figure 5; Figure 7b is a longitudinal section through the indicating means of Figure 7a; Figure 8a is an enlarged view of the part "Y" of Figure 6;; Figure 8b is an axial view of the indicating means of Figure 8a.

Referring firstly to Figure 1 of the drawings, a propeller shaft indicated generally at 10 comprises a first shaft part 11 and a second shaft part 12 which are connected to one another for torque transmission and sliding movement axially relative to one another by a length-adjusting means which comprises a journal or spigot 13 provided on the shaft part 11 fitting within a sleeve 14 connected to the shaft part 12. The journal 13 and sleeve 14 have inter-engaging profiles, e.g. interfitting splines, which provide the torque-transmitting and relatively axially movable connection therebetween.At their ends remote from one another, the shaft parts 11, 12 are provided with universal joint yokes 15, 15a respectively which in turn, by way of cross-members of the type conventional in Hookes universal joints, are connected to further joint yokes provided with drive flanges 16 for connection to further torque-transmitting parts.

A cover tube 18 extends over the exterior of the torque-transmitting shaft, being non-rotatingly connected at 17 to the first shaft part 11 and extending to a position adjacent the joint yoke 15a connected to the second shaft part 12.

At its free end, the cover tube 18 has a support 20 which ensures equal spacing of the cover tube from the outer surface (indicated at 35) of the shaft part 12, the support also forming a seal to prevent ingress of dirt to the interior of the cover tube 18 and, particularly, access of dirt to the sliding connection between the journal 13 and sleeve 14. As shown in Figure 1, the shaft as a whole is in its shortest condition, i.e. the journal 13 is slid as far as possible into the sleeve 14.

The shaft shown in Figure 2 is similar to that shown in Figure 1 and the same reference numerals are used for parts which are of corresponding or analogous construction or function. In the embodiment of Figure 2, however, the cover tube 18 has a non-rotating connection, at 17a, to the second shaft part 12 adjacent its connection to the sleeve 14 instead of to the first shaft part 11. To protect the sliding connection between the sleeve 14 and journal 13, a protective tube 11a is connected to the shaft part 11 and extends over the exterior of the sleeve 14. The free end of the cover tube 18 is supported relative to the external surface of the second shaft part 12 by a support 20, but it will be appreciated that, because the cover tube is connected to the second shaft part 12, no relative axial movement between the cover tube and shaft part takes place at the support 20.

It will be appreciated that, when the shaft 10 is subject to torque, its ends as represented by the drive flanges 16 twist relative to one another with a certain deflection. Parts of the shaft between the flanges are twisted relative to one another to a lesser extent. As the cover tube 18, constituting a holding element, does not participate in transmission of torque and thus does not twist, the position of any point at the free end of the cover tube changes in the circumferential direction relative to the adjacent shaft parts. Such twisting may occur in the range of elastic or plastic deformation of the shaft 10: in the case of elastic deformation the material of the shaft returns to its original condition after the load has been removed, whereas in the case of plastic deformation some twist will remain even after the load has been removed.The shaft may be subjected to undesirable overload even by elastic deformation, but no identifiable evidence of such overload and deformation after the load has been removed.

The present invention permits even deformations within the elastic range to be indicated permanently, if such deformations exceed a predetermined value. To this end, cooperating elements of indicating means are provided between the free ends of the cover tube and the adjacent shaft part.

The indicating means is shown generally at 19 in Figures 1 and 2, and in detail in Figures 3 and 4, and comprises an element in the form of a pin 21 extending radially outwardly from the surface 35 of the shaft part 11, the pin 21 being held by a holding means 22 which may, for example, be welded to the shaft part 12. The cover tube 18 holds two capsules 23, 24 containing a die, disposed on opposite sides (in the circumferential direction of the shaft) of the pin 21, with spaces 30 therebetween. The capsules 23, 24 are preferably of a brittle material, e.g. glass, and are filled with a liquid dye 31.

The dye capsules 23, 24 are each held at their ends in capsule holding means 25. The disposition and length of the capsules is such that they can be reached by the pin 21 even if relative movement axially of the shaft occurs between the pin and capsules as a result of change in the length of the shaft in the Figure 1 embodiment. The capsule holding means 25 are formed by radially inwardly extending indentations 26 of the cover tube 18. The indentations 26 afford recesses 27 through which the capsules 23, 24 can be reached by the pin 21 upon rotation of the shaft relative to the cover tube, and the recesses 27 also retain an absorbent material 28 which lies on the outer surface of the cover tube 18 in contact with the capsules 23, 24. A cover 29, of transparent material, e.g.

plastics such as "Plexiglass", protects the absorbent material from dirt and water.

The indicating means comprising the capsules 23 and 24, the absorbent material 28, and its cover 29 may also subsequently be inserted into or replaced in suitable indentations 26 provided in the cover tube 18 (what does this mean?). The nature of the absorbent material 28 may be such that it absorbs only the liquid dye 31, (which may, for example, be a coloured oil) but not water spray. The dye capsules 23, 24 may be pressed or glued into the cover tube, or moulded into the latter if the latter is made of plastics material.

In this way it is possible to provide a readily visible indication of torque overload by mechanical means which, in borderline cases, avoids any problems of assessment. By selecting a suitable colour for the dye, for example the alarm colour red, torque overloading is indicated in an obviously visible way.

Depending on the requirements, a very slight relative movement in the circumferential direction between the pin 21 and the dye capsules may be sufficient to break the latter to indicate overloading, or a greater relative movement may be required. When one or both of the capsules 23, 24 breaks, the dye 31 is used up, which means that indication given by the dye capsules cannot be concealed without replacement of the entire assembly of dye capsules and absorbent material.

Referring now to Figure 5 of the drawings, this shows a further embodiment of propeller shaft according to the invention. Once again, parts of the shaft corresponding to those appearing in the embodiments of Figures 1 and 2 are identified by the same reference numerals. In the embodiment of Figure 5, the holding element is provided by an indicating shaft 32 which is disposed within the shaft part 12, the indicating shaft being non-rotatingly connected to the shaft part 12 at one end by a connection 17b, and being supported at a position between its ends relative to the shaft part 12 by a support element 33 extending radially inwardly from the shaft part. The support element 33 provides against displacement of the indicating shaft 32 when the propeller shaft is rotating at high speeds.The indicating shaft 32 is free of torsion, so that torsion of the shaft part 12 under load is visible as relative displacement between the end of the indicating shaft remote from its connection 17b, and the adjacent part of the shaft part 12.

For this purpose, indicating means shown generally at 19 is provided, such indicating means being disposed in an aperture at the centre of the joint yoke 15a and being shown in greater detail in Figures 7a and 7b.

Referring to Figures 7a and 7b, these show the end of the indicating shaft being provided with a radially extending pin 21 having a head 37. An indicating unit 34 is inserted into a recess extending axially into the centre of the joint yoke 15a, the indicating unit supporting a pair of dye capsules 23, 24 in positions such that they are circumferentially spaced from the head 37 of pin 21 when the shaft is not subject to any torque. The capsules 23, 24 are accessible by the pin head 37 through recesses 27a when the limit of acceptable twisting of the shaft is reached.Strips of absorbent material 28a disposed around the recesses 27a are in contact with a further piece of absorbent material 28 which lies immediately beneath a transparent cover portion 29 of the indicating unit 34, so that when one or both of the capsules 23, 24 is broken and the dye 31 emerges therefrom, the dye is guided underneath the cover 29 to provide a clear visible indication that overload has occurred. The transparent cover 29 may, as for the rest of the indicating unit as in the illustrated embodiment, comprise a plastics material such as

Referring now to Figure 6 of the drawings, this shows a further embodiment of propeller shaft according to the invention wherein the holding element is constituted by an indicating shaft 32 extending through the centre of the torque-transmitting shaft.In this embodiment, the indicating shaft 32 extends throughout substantially the entire length of the two relatively axially movable shaft parts 11, 12 so that, as compared with the embodiment of Figure 5, a given torque loading in the propeller shaft achieves a relatively greater twisting of the free end of the indicating shaft relative to the adjacent part of the torquetransmitting shaft. The necessary relative axial movement between the indicating shaft and the torque-transmitting shaft may be provided at the non-rotating connection 17c therebetween, which may be constituted by a squared head on the indicating shaft engaging in a square section aperture extending axially through the shaft part 11. Alternatively, relative axial movement may be provided for at the indicating means at the other end of the indicating shaft.As in the embodiment of Figure 5, a support element 33 is provided for supporting the indicating shaft within the torque-transmitting shaft, to increase the critical speed of the indicating shaft.

The indicating means shown generally at 19a in Figure 6 may be as illustrated in Figures 8a and 8b, which show only the portion Y of Figure 6. The indicating means comprises a pin 21 extending radially outwardly from the indicating shaft 32, through an aperture 38 in the joint yoke 15a. The aperture 38 permits some movement of the outermost end of the pin 21 circumferentially of the joint yoke, but restrains the pin 21 against movement axially of the shaft, thus restraining axial movement of the adjacent end of the indicating shaft 32 and imposing axial movement of the opposite end of the indicating shaft at the connection 17c relative to the shaft part 11 when the overall length of the propeller shaft changes.On the exterior of the joint yoke 15a there is provided an indicating unit which contains dye capsules 23, 24 arranged to be broken by the head of the pin 21 upon circumferential movement of the head of the pin relative to the capsule beyond a predetermined amount corresponding to acceptable twisting and hence torque in the propeller shaft. The indicating unit containing the capsules 23, 24 also contains an absorbent material for the dye therefrom, and a transparent cover so that the release of dye is visible when it occurs. The aperture 38 is covered by the indicating unit so that access of dirt to the interior of the propeller shaft is not possible.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A shaft for torque transmission, having a holding element which extends coaxially relative to the shaft and is not subject to torque, one end of the holding element being non-rotatingly connected to the shaft, and the other end of the holding element and the shaft adjacent such other end being provided with cooperating elements of indicating means for indicating deformation of the shaft caused by torque, wherein the cooperating elements of the indicating means comprise at least one member containing a marking material and an element arranged to engage said at least one member upon shaft overload to cause release of said marking material.

2. A shaft according to claim 1 wherein said marking material comprises a dye and easily breakable capsules thereof are disposed on opposite sides, circumferentially of the shaft, of said element.

3. A shaft according to claim 2 wherein the dye capsules are held in axially extending, radially inwardly facing recesses of the holding element.

4. A shaft according to claim 3 wherein said element is associated with the shaft part disposed radially inwardly of the holding element, and extends radially outwardly into the region of the dye capsules.

5. A shaft according to any one of claims 2 to 4 wherein there is a space between said element and each of the capsules in the circumferential direction of the shaft, when the shaft is not subject to any torque.

6. A shaft according to any one of claims 2 to 5 wherein the dye capsules are covered by an absorbent material.

7. A shaft according to claim 6 wherein the absorbent material is covered by a transparent cover.

8. A shaft according to claim 6 or claim 7 wherein the dye capsules are in contact with each other by way of the absorbent material.

9. A shaft according to any one of claims 2 to 8 wherein the dye capsules are of a brittle material and are filled with a liquid dye.

10. A shaft according to any one of the preceding claims wherein the holding element comprises a cover tube embracing the shaft along at least part of its length.

11. A shaft according to any one of claims 1 to 9 wherein the holding element comprises an indicating shaft disposed within the torque-transmitting shaft which is of hollow configuration.

12. A shaft according to claim 10 wherein the shaft comprises two parts connected to one another by length-adjusting means, the cover tube being connected to one shaft part, extending over the length-adjusting means, and extending to a position in the region of the free end of the other shaft part.

13. A shaft according to claim 12 wherein the member or members containing marking material have a length corresponding to the length adjustment provided by the length-adjusting means.

14. A shaft according to claim 10 wherein the shaft comprises two parts connected to one another by length-adjusting means, and one end of the cover tube is connected to a shaft part in the region of the length adjusting means, the elements of the indicating means being carried by the other end of the cover tube and an adjacent region of the same shaft part.

15. A shaft according to claim 10 or any claim appendant thereto wherein the indicating means are arranged in an annular gap radially between the cover tube and adjacent part of the shaft.

16. A shaft according to claim 11 wherein the indicating shaft is nonrotatingly connected to a part of the torque-transmitting shaft at the greatest possible distance from its free end at which one of the co-operating elements of the indicating means is carried.

17. A shaft according to claim 11 or claim 16 wherein the indicating means are disposed in an axially facing aperture at the free end of the shaft part.

18. A shaft according to claim 11 or claim 15 wherein the element of the indicating means associated with the indicating shaft extends radially outwardly from the indicating shaft, into an aperture in the adjacent part of the torquetransmitting shaft, with which the member or members containing marking material are associated.

19. A shaft according to claim 11 wherein the indicating shaft is axially movable relative to the part of the torque-transmitting shaft to which it is nonrotatingly connected or relative to the element of the indicating means with which it is associated.

20. A shaft according to claim 18 and claim 19 wherein the radially outwardly extending element of the indicating means is guided in the aperture to be movable circumferentially only of the associated part of the torque-transmitting shaft.

21. A shaft according to claim 11 or any claim appendant thereto wherein the indicating shaft, between its connection to a shaft part and the indicating means, is supported by at least one supporting element.

22. A shaft according to any one of the preceding claims wherein one of the elements of the indicating means forms part of or is disposed in the region of a window provided in a shaft part or cover tube.

23. A shaft according to claim 22 wherein the window is closed by a piece of transparent plastics material.

24. A shaft according to any one of the preceding claims which is a propeller shaft for a vehicle driveline.

25. A shaft substantially as hereinbefore described with reference to any one of the accompanying drawings.

26. Any novel feature or novel combination of features described herein and/or in the accompanying drawings.