Flexible protective bellows

Abstract: A flexible protective bellows (16) for enclosing a universal joint (12) of a vehicle transmission is designed so that alternate folds (16A,16C,16E) are of different shape from the intervening ones (16B,16C,16E) are of different shape from the intervening ones (16B,16D,16F). This reduces wear between the peaks (22) of adjacent folds when the bellows is compressed. The troughs (24) are formed with loops (34) to reduce wear when the bellows is stretched. Various means for securing the bellows in its fixing groove (18) in the housing (14) of the universal joint are also disclosed as are means for incorporating a toothed ring for use in speed measurement for the vehicle's ABS system.

Description: The invention relates to a flexible protective bellows, comprising a plurality of turns or folds arranged next to each other along the length of the bellows and projecting outwardly of the bellows and integrally connected to each other by troughs projecting inwardly of the bellows, alternate ones of the turns or folds being triangular-shaped in cross-section and at least one intervening turn or fold being convexly curved in cross-section whereby to minimise abrasive contact between adjacent turns or folds. Such a bellows is shown in US-A-4 895 550. In this known form of bellows, however, the bellows turns or folds are not arranged regularly along the length of the bellows. At one end of the bellows, the bellows turn there is connected to the next bellows turn along the length of the bellows by an extended trough whose dimension along the length of the bellows is substantially the same as the corresponding dimension of the turns or folds. Such an arrangement is unsatisfactory in the case where the bellows has significant length and only a gradually changing or tapering diameter along its length. The extended trough at one end of the bellows would in such a case provide distortion when the bellows is angularly bent. The invention aims to overcome this problem. According to the invention, therefore, the bellows as first set forth above is characterised in that the triangularly-shaped turns or folds and the curved turns or folds are regularly distanced from each other along the length of the bellows. A flexible protective bellows embodying the invention and made of thermoplastic material and for use in protecting universal joints in motor vehicle transmissions will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic side view showing, in simplified form, a universal joint incorporated in a front wheel drive shaft of a motor vehicle transmission and showing part of one of the bellows; Figure 2 shows the bellows of Figure 1 in compressed form; Figure 3 is a diagrammatic view corresponding to part of Figure 1 but showing a prior art form of bellows construction in compressed form; Figure 4 shows, to an enlarged scale, a sharp bend in the material of the bellows, at the trough between adjacent folds of the bellows, illustrating how wear can develop; Figure 5 is similar to Figure 4 but shows a greater degree of wear; Figure 6 shows a modification to the bend in the bellows illustrated in Figures 4 and 5 for the purposes of reducing wear; Figures 7 and 8 show the bellows construction of Figure 6 in stretched and compressed configurations; Figures 9 to 14 show modified forms of the construction shown in Figure 6; Figure 15 shows a view corresponding to Figure 1 but with the bellows modified in accordance with Figure 6; Figure 16 shows to an enlarged scale and in sectional form a mounting groove for use in securing the bellows on the universal joint; Figures 17 and 18 are perspective sectional views corresponding to Figure 16 but showing modified constructions; Figure 19 corresponds in general form to Figure 16 but shows a modified form of the groove and also shows part of the bellows being clamped in position; Figure 20 shows the part of the bellows of Figure 19 in un-clamped configuration; Figure 21 corresponds to Figure 19 but shows a prior form of construction; Figures 22 and 23 correspond to Figures 19 and 20 but show different configurations for the bellows; Figures 26 and 27 show an alternative means of clamping the bellows in position; Figure 28 corresponds to Figure 19 but shows a method of fixing the bellows in position by an in-situ moulding process; Figure 29 corresponds to Figure 28 but shows how a moulded clamping ring for holding the bellows in position may also form a toothed ring for use in controlling the vehicle's ABS system; Figure 30 shows how the toothed ring of the ABS system may be incorporated in the actual bellows construction; Figure 31 is a partial end view of the teeth of the ring shown in Figure 30; Figure 32 shows a heat-responsive clamping ring which may be used for clamping the bellows in position; and Figure 33 is a view corresponding to Figure 1 but showing a modified form of bellows and also incorporating a clamping ring arranged to act as a toothed ring for the ABS system. As shown diagrammatically in Figure 1, a drive shaft 10 for the front wheel drive transmission of a motor vehicle drives the road wheel through a universal joint indicated generally at 12 and including a housing 14. The universal joint is enclosed within a bellows which is made of thermoplastic material and part, only, of which is shown at 16. At one end, the bellows is secured (in the manner to be explained) within a groove 18 on the outside of the housing 14. At the other ends, the bellows is secured at 20 to the shaft 10. The bellows 16 is moulded from thermoplastic material and is configured to provide a plurality of turns or folds 16A, 16B..16F, each of which has a peak (e.g. as shown at 22) and each of which is connected to the adjacent fold by a trough (e.g. at 24). As is clear from Figure 1, the configuration of the folds 16A to 16F varies. The folds 16A,16C and 16E have sharply pointed peaks while the intervening folds 16B,16D and 16F have rounded peaks. The provision of such alternately different configurations for the folds is advantageous in reducing wear when the bellows becomes compressed in operation (during articulation of the joint 12). Figure 2 shows in diagrammatic form the configuration which the bellows takes when compressed. Because of the configuration of the folds, the compressed folds are still spaced apart in the region of their peaks. This contrasts with what is shown in Figure 3. Figure 3 illustrates a previously known type of bellows in which all the folds are of the same type of configuration (generally rounded in this example). When such a bellows is compressed, as shown in Figure 3, the material of the bellows comes into forceful contact in the area of the peaks of the folds. It is found in practice that this can cause rapid wearing of the material. Figure 4 illustrates one of the troughs 24 of Figure 1 to an enlarged scale. It is found that excessive wear can occur as shown at 30. This is due to fatigue in the material caused primarily by stretching. Figure 5 shows how an actual split 32 in the material can occur at this point. In order to deal with this, the troughs of the bellows may be constructed as shown in Figure 6 where the material is moulded to form a loop 34 at each trough. When the bellows is stretched, as shown in Figure 7, the loop 34 is expanded but distributes the stretching action so that the risk of fatigue or a tear is minimised. When the bellows is compressed, as shown in Figure 8, the loop 34 becomes closed with faces 36 and 38 abutting each other. This abuttment action limits the amount of stretching of the material forming the loop 34 (as compared with that which would occur with a configuration such as shown in Figure 4). The thermoplastic material within the loop 34 is hardly strained any more than it is in its relaxed configuration (Figure 6). In other words, the curved plane 40 (Fig. 8) constituting the neutral plane of bending has nearly the same configuration as in Figure 6. In order to obtain optimum operation, it is important that the dimension A (Fig. 6) should always be less than the dimension B. Figures 9 to 14 show alternative forms which the loop 34 of Figure 6 can take. Figure 15 corresponds to Figure 1 but shows the bellows 16 as incorporating loops 34 in the troughs of the bellows. Figures 1 and 15 show the bellows as anchored on the bowl 14 by being fitted within a groove 18. It is important that the bellows is securely anchored in the groove 18, and to the shaft 10, so as to prevent any relative movement taking place. This is particularly likely to occur when the material of the bellows is cold and relatively stiff. Figure 16 is a cross-section through the housing 14 (Figures 1 and 15) but showing a modified form for the groove 18. As shown, the groove is formed with teeth 42 and with raised shoulders 44. The purpose of these configurations, particularly the teeth 42, is to pierce the thermoplastic material of the bellows when it is anchored in the groove 18 so as to avoid any relative movement between the housing 14 and the bellows. A similar form of groove may be produced on the shaft 10 in the region of the join 20 (Figures 1 and 15), for the same purpose: that is, to prevent relative movement in this region between the bellows and the shaft. Figure 17 shows a modified form which the groove can take. Here, teeth 46 are formed along the top of the walls defining the groove. Again, the purpose is the same: that is, to pierce the thermoplastic material of the bellows so as securely to lock it in position. Figure 18 shows a further possible arrangement in which there are teeth 48 along one side of the groove and a plain shoulder 50 along the other. Various methods of locking the bellows within the groove 18 will now be described. Figure 19 shows one such form. Here, the configuration of the bellows at the end which is to be fitted to the housing 14 is such as to form a rounded profile 52 (Figure 20) which extends over a width greater than the width of the throat 18 (Figure 19). Therefore, the edges along the throat 18 pierce into the thermoplastic material when it is clamped in position on the housing 14 by means of a clamping ring shown diagrammatically at 54. Such an arrangement is found to be advantageous as compared with an arrangement shown diagrammatically in Figure 21 where the bellows is profiled, at 56, to match the shape of the trough 18; such an arrangement does not give adequate security for the fixing of the bellows to the housing 14. Figures 22 and 23 correspond to Figures 19 and 20 respectively and show a modified configuration for the bellows. Figures 24 and 25 correspond with Figures 19 and 20 and show a further possible modification. In Figures 22 to 25, items corresponding to those in Figures 19 and 20 are similarly referenced. In the arrangement shown in Figures 19,22 and 24, the grooves 18 may be constructed as shown in Figure 18,19 or 20. The profiles shown in Figures 20,23 and 25 can also be used at the other end of the bellows, where it is fitted onto the shaft 10. Figure 26 shows another method of fitting the bellows to the housing 14. Here, special heating jaws 56 are applied to the bellows after it has been placed on the housing 14 and with a profile 58 on the thermoplastic material located in the groove 18. Heating is applied to the thermoplastic material which causes the material to fuse to the material of the housing. Figure 27 shows a modified form of arrangement in which the groove 18 has a dovetail-shaped form in cross-section, into which the thermoplastic material fuses when heating is applied by the jaws 56. This gives better security of fixing. After the heating and fusing operation has taken place, the jaws 56 are removed. The jaws may be in the form of two semi-circular parts defining an inside diameter of appropriate size to embrace the end of the bellows when in position on the housing 14. Clearly, a similar arrangement can be used to attach the other end of the bellows to the shaft. Figure 28 shows another possible arrangement for securing the bellows in position on the housing 14. Here, a clamping ring 58, encircling the material of the bellows, is formed in situ by a moulding operation. As shown, the bellows is placed over the housing 14 with a profile 60 engaging in the groove 18. A metal mould 62 is then placed over the outside of the bellows (for example, a two-part mould may be used). By means of an injection moulding process, via an inlet 64, the clamping ring 58 is moulded in position around the complete circumference. The mould is then removed. Such a moulding operation may also be used to attach the other end of the bellows to the shaft. Vehicles employing ABS braking systems require a means of detecting the speed of rotation of each road wheel and such means may be in the form of a toothed wheel located adjacent to and rotating with the road wheel and cooperating with a sensor (e.g. optical or magnetic) to measure the speed of rotation. Figure 29 shows how such a toothed ring may also carry out the function of clamping the bellows on the housing 14. Thus, Figure 29 shows the bellows on the outside of the housing with a profile 60 located in the groove 18 and held in position by a circumferentially extending extension 62 of a toothed ring 64 for the ABS system. The toothed ring 64 has teeth 66 which interact with an appropriate sensor as the housing 14 rotates with the wheel. Such a toothed ring, including integral extension 62, may be formed in situ by a moulding operation corresponding to that shown in Figure 28. With the arrangement shown in Figure 29, an optical-type sensor would normally be used. However, it would be possible to incorporate metal facets into the teeth 66 to permit magnetic sensing. Figure 30 shows a modified arrangement in which the toothed ring for the ABS system is constituted by the end of the bellows itself. During the moulding operation for producing the bellows, the ABS toothed ring 64 is integrally moulded to produce teeth 66. If the rotation of the toothed ring is to be achieved by use of a magnetic sensor, metal facets such as shown at 68 can be incorporated. Figure 31 shows the diagrammatic end view of the toothed ring 64. In the case shown in Figures 30 and 31, the bellows would be fixed onto the housing 14 by any of the means already described with its profile 60 engaging the groove 18. Figure 32 shows one form which a clamping ring, such as the clamping ring 54 shown in Figures 19,22 and 24, may take. Here, part 70 of the clamping ring is made of ordinary steel. The ring is completed by a hook 72 which is made of metal which contracts in response to the application of heat and remains contracted. Such an arrangement therefore can be designed so as to clamp the end of the bellows firmly in position. Another alternative is to make the entire clamping ring from such heat sensitive material. Reference is made to French Patent Application FR-A-2640 331 in this respect. An arrangement such as shown in Figure 32 is advantageous for automatic assembly of bellows onto housings 14. Clearly, similar clamping rings may be used to secure the other end of the bellows onto the shaft. Figure 33 corresponds generally to Figures 1 and 15 but shows a modified form of the bellows of Figure 1 and also incorporating loops 34 of the type shown in Figure 6 and held in position on the housing 14 by a clamping ring of the type shown in Figure 29 and incorporating a toothed ring for the ABS system.

Claims: A flexible protective bellows, comprising a plurality of turns or folds (16A,16B...) arranged next to each other along the length of the bellows and projecting outwardly of the bellows and integrally connected to each other by troughs (24) projecting inwardly of the bellows, alternate ones of the turns or folds (16A,16C,16E..) being triangular-shaped in cross-section and at least one intervening turn or fold (16B,16D,16F..) being convexly curved in cross-section whereby to minimise abrasive contact between adjacent turns or folds (16A,16B,16C...), characterised in that the triangularly-shaped turns or folds (16A,16C,16E) and the curved turns or folds (16B,16D,16F...) are regularly distanced from each other along the length of the bellows. A bellows according to claim 1, characterised in that the troughs (24) between adjacent turns or folds (16A,16B,16C...) are shaped to reduce wear in the event of longitudinal stretching of the bellows. A bellows according to claim 1 or 2, characterised in that at each trough (24) the two folds (e.g. 16A,16B) meeting there are joined together by an integrally connected loop (34) extending inwardly of the bellows. A bellows according to claim 3, characterised in that the loop (34) of each trough (24) is re-entrantly shaped and has a re-entrant mouth whose parallel defining sides (36,38) are respectively constituted by the folds (e.g. 16A,16B) meeting at that trough (24). A bellows according to claim 4, characterised in that the parallel sides (36,38) of each loop (34) are constituted by relatively flat faces of the material which abut upon compression of the bellows. A bellows according to any one of claims 3 to 5, characterised in that the width across each loop (34) is greater than half the width across the re-entrant mouth. A bellows according to any preceding claim, characterised in that it carries a circumferentially extending ring (64) formed with discrete teeth for use in measuring the speed of rotation of the mechanism. A bellows according to claim 7, characterised in that the discrete teeth incorporate metal inserts (68). A bellows according to any preceding claim, characterised by a clamping ring (58) which is moulded in situ in position around the circumference of an end region of the bellows for securing it in position.

Inventors: LALLEMENT SERGE, LALLEMENT, SERGE
Applicants: DRAFTEX IND LTD, DRAFTEX INDUSTRIES LIMITED
Application year: 1991
Main classification: F16J3
IPC codes: F16J15, F16D3, F16J3