Protective bellows

Abstract: A protective bellows (28) is disclosed for protecting the axially movable rod (18) of a steering mechanism which has an angularly movable rod end (22). The bellows has a fixing collar (30) attached to the end of a casing (17) from which the steering rod (18) axially extends, and another fixing collar (32) clamped to the rod end (22). Bellows turns (28A...28N) extend between these fixing collars (30,32) but are interrupted by an integral substantially cylindrical skirt portion (34) which is sized to make contact with the outside of the joint (26) connecting the rod end (22) to the steering rod (18). The skirt portion (34) ensures that the bellows turns are substantially undistorted by large angular movement of the rod end (22). Adjacent bellows turns (e.g. 28A,28B) have different cross-sectional sizes so that their peaks and troughs have different diameters. This reduces the compressive forces acting between adjacent turns when the bellows is compressed by sliding of the steering rod (18).

Description: The invention relates to protective bellows. A protective bellows embodying the invention, and to be described in more detail below by way of example, is for protecting the steering mechanism of a motor vehicle. Protective bellows according to preamble of claim 1 are known from FR-A-2687753 or EP-A-327347. According to the invention, there is provided a protective bellows for protecting an axially movable member which has an angularly movable end portion, comprising integral fixing means for fixing one end of the bellows to mounting means with respect to which the member is axially movable, and integral fixing means for fixing the other end of the bellows to the angularly movable end portion of the member, characterized in that the bellows incorporates a substantially axially directed skirt portion sized to seat itself and be located on the part of the axially movable member adjacent its junction with the angularly movable end portion, the bellows having a first plurality of bellows turns extending between one fixing means and the skirt portion and a second plurality of bellows turns extending between the skirt portion and the other fixing means, the bellows turns remaining out of contact with the remaining portions of said member and of its end portion. According to the invention, there is also provided a protective bellows for protecting an axially movable rod member of a steering mechanism which carries a joint connected to a rod end linked to a steerable road wheel of the vehicle, the joint permitting the rod end to move angularly with respect to the axially movable rod member, the bellows comprising a first fixing collar at one of its ends for securing that end to the steering mechanism from which extends the axially movable rod member, a second fixing collar at the other of its ends for securing that end to the angularly movable rod end, and an intermediate generally cylindrically shaped skirt portion which contacts the outside of the joint, the bellows also incorporating a first plurality of bellows turns extending integrally between the first fixing collar and one axial end of the skirt portion and a second plurality of bellows turns extending from the other axial end of the skirt portion to the second fixing collar. A protective bellows embodying the invention, and for protecting the steering mechanism of a motor vehicle, will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a cross-section through a known form of bellows fitted in position on the steering mechanism of the motor vehicle; Figure 2 corresponds to Figure 1 and shows the configuration which the known bellows of Figure 1 adopts when the steering is turned through a sharp angle (only a half-section of the bellows being shown for simplicity); Figure 3 is a view corresponding to Figure 1 but showing one form of bellows embodying the invention; Figure 4 corresponds to Figure 2 and shows the configuration which the bellows of Figure 3 adopts when the steering is turned through the sharp angle; Figure 5 is a cross-section through part of a modified form of the bellows of Figures 3 and 4; Figure 6 corresponds to Figure 5 but shows a further modified form of the bellows; Figure 7 is a view corresponding to part of Figure 4 but showing the addition of means defining an air passage along part of the bellows; and Figure 8 is a cross-section on the line VIII-VIII of Figure 7. Figure 1 shows a known form of bellows 10 fitted in position on the steering mechanism 12 of a motor vehicle. As shown, the bellows 10 extends between two fixing collars 14 and 20. Fixing collar 14 is secured to a circumferential mounting surface 16 forming the end of a casing 17 of the steering mechanism. Fixing 20 is secured to the end 22 of the steering rod 18 of the steering mechanism. The collars 14 and 20 may be clamped in position by clamping rings not shown. The longitudinal or axial position of the rod 18 is adjusted by the mechanical or hydraulic mechanism within the casing 17 and transmits its movement to one of the front wheels of the vehicle to which it is connected by the rod end 22. The rod end 22 can move angularly relative to the rod 18, being connected to the rod 18 by a joint 26. A similar rod projects from the other end of the casing 17 and is similarly adjusted, and, in turn, adjusts the position of the other front road wheel. A similar bellows is fitted at that end of the casing. As shown in Figure 1, the bellows 10 comprises a plurality of substantially identical bellows turns 10A,10B,10C...10M which extend from the fixing collar 14 towards the fixing collar 20. However, the final bellows turn 10M is connected to the fixing collar 20 by an extension 24 of this turn, the extension 24 taking account of the difference in diameter between the two fixing collars 14 and 20. Figure 2 shows the configuration adopted by the known bellows 10 when the rod end 22 is turned through a sharp angle. As indicated, this causes the extension 24 to exert a pull on the adjacent bellows turns 10L and 10M, buckling and distorting them and bringing the troughs of these turns into, or nearly into, contact with the outside of the casing of the joint 26. This buckling and distortion, and partial contact with the end cap 26, is unsatisfactory. As shown in Figure 3, the bellows 28 embodying the invention has fixing collars 30 and 32 corresponding to the fixing collars 14 and 20 of the bellows of Figures 1 and 2. However, the bellows 28 is arranged in two portions A and B which are integrally interconnected by a skirt portion 34. The portion A of the bellows is made up of bellows turns 28A,28B,28C.... 28K, the last turn 28K having an extension 36 which is connected to the skirt portion 34 by a trough 38. The portion B comprises bellows turns 28L,28M and 28N. Bellows turn 28L is connected to the skirt portion 34 by a shallow trough 40. Bellows turn 28N has an extension portion 42 which is connected to the fixing collar 32. The skirt portion 34 is cylindrical in shape and is sized so as to seat itself on the outside of the casing 26. The troughs 38 and 40 locate the skirt portion on the casing 26 and provide a clamping action. The number of bellows turns within the portions A and B can be varied as necessary. The bellows turns 28A... 28K of the portion 28 are arranged so that the peaks of alternate turns have the same diameter as each other but this diameter is different from the diameter of the peaks of the intervening turns. Similarly, the troughs of alternate turns have the same diameter but this diameter is different from the diameter of the intervening turns. Therefore, when the rod 18 moves to the left (as viewed in the Figures) relative to the casing 17, thus compressing the turns 28, the peaks of adjacent turns do not come into contact with each other (because they are of different diameter); similarly, the troughs of adjacent turns do not come into contact with each other. This reduces the pressure generated between adjacent bellows turns. Figure 4 shows the configuration which the bellows 28 adopts when the rod end 22 is turned through a sharp angle. Because the skirt portion 34 is always in contact with the outside of the joint 26, substantially no distortion or buckling of the bellows occurs. The bellows turns over the portion A are substantially unaffected by the angularity of the rod end 22. The angularity of the rod end 22 is accommodated by the bellows turns in the portion B. The bellows turns within the portion A are shown as having a cylindrical generatrix. However, instead they may have a slightly conical generatrix. The bellows turns within the portion B can be similarly arranged. The outer diameter of the bellows turns 28L to 28N is preferably between 0.7 and 1.2 times the outer diameter of the skirt portion 34. Figures 5 and 6 show different arrangements of bellows turns within the portion 28 of the bellows of Figures 3 and 4. In Figure 5, alternative bellows turns have the same outer diameter but this diameter differs from the outer diameter of the peaks of the intervening turns. However, in contrast to the bellows of Figures 3 and 4, all the troughs have the same diameter. In Figure 6, all the peaks have the same diameter, in contrast to the bellows of Figures 3 and 4, but the troughs of alternate turns have a diameter which differs from the diameter of the intervening turns. The arrangements of Figures 5 and 6 thus provide at least a partial reduction of the pressure which each turn exerts on the next turn during compression of the bellows. Because the skirt 34 is in contract with the joint 26, the region 50 within the bellows portion A (Figs. 3 and 4) is substantially sealed off and isolated from the region 52 within the bellows portion B. In order to prevent any unsatisfactory build-up of pressure difference between the regions 50 and 52, an air passage 60 (Fig. 7) may interconnect the two regions. Figure 8 shows how the air passage 60 may be produced by forming a groove in the material of the skirt 34. A second groove may be provided to constitute a second air passage 62.

Claims: A protective bellows for protecting an axially movable member (18) which has an angularly movable end portion (22), comprising integral fixing means (30) for fixing one end of the bellows to mounting means (16) with respect to which the member (18) is axially movable, and integral fixing means (32) for fixing the other end of the bellows to the angularly movable end portion (22) of the member (18), characterised in that the bellows incorporates a substantially axially directed skirt portion (34) sized to seat itself and be located on the part (26) of the axially movable member (18) adjacent its junction with the angularly movable end portion (22), the bellows having a first plurality of bellows turns (A) extending between one fixing means (30) and the skirt portion (34) and a second plurality of bellows turns (B) extending between the skirt portion (34) and the other fixing means (32), the bellows turns remaining out of contact with the remaining portions of said member (18) and of its end portion (22). A bellows according to claim 1, characterised in that the skirt portion (34) incorporates at least one radially directed at least partially circumferentially extending formation for locating the skirt portion axially with respect to the said part (26) of the member. A bellows according to claim 1 or 2, characterised in that the axially movable member (18) is a rod member of a steering mechanism which carries a joint connected to a rod end (22) which is linked to a steerable road wheel of a vehicle and which constitutes the angularly movable end portion (22). A bellows according to any preceding claim, characterised by means defining an air passage (60,62) extending between two portions (12,52) within the interior of the bellows which are otherwise separated from each other by contact of the skirt portion (34) with the said part (26) of the member. A bellows according to any preceding claim, characterised in that there is a relatively large number of bellows turns in the first plurality (A) and a relatively small number of bellows turns in the second plurality (B). A bellows according to any preceding claim, characterised in that adjacent bellows turns in the first plurality (A) are differently sized so as to reduce compressive forces acting therebetween when the bellows is longitudinally compressed by axial movement of the said member (18). A bellows according to any of claims 1 to 5, characterised in that the diameter of the peak of each bellows turn in the first plurality (A) differs from the diameter of the peak of the adjacent bellows turn. A bellows according to claim 6 or 7, characterised in that the diameter of the trough of each bellows turn of the first plurality (A) differs from the diameter of the trough of the adjacent bellows turn. A bellows according to any one of claims 6 to 8, characterised in that the diameter of the peak of each bellows turn of the first plurality (A) is substantially the same as the diameter of the peak of the next alternate bellows turn of that plurality. A bellows according to any one of claims 6 to 9, characterised in that the diameter of the trough of each bellows turn of the first plurality (A) is the same as the diameter of the trough of the next alternate bellows turn of that plurality.

Inventors: BOUHOUR JEAN LUC, BREHERET JOEL, BOUHOUR, JEAN LUC, BREHERET, JOEL
Applicants: DRAFTEX IND LTD, DRAFTEX INDUSTRIES LIMITED
Application year: 1995
Main classification: F16J3
IPC codes: F16J3, B29D23, F16L35, F16D3