Imported: 10 Mar '17 | Published: 27 Nov '08
USPTO - Utility Patents
In a sleeve rolling-lobe flexible member air spring (2) at least one end section (4a, 4b) of the sleeve rolling-lobe flexible member (4) is to be attached in a reliable manner form tight, pull tight and pressure tight to a connecting part (air spring cover, 8 and/or roll-off piston, 10) by means of a clamp ring (6). The connecting part (8, 10) has an attachment slot (12) having the following characteristics: (a) the slot (12) has a truncated cone-shaped cross section, (b) the base (14) of the slot (12) is cylindrical, and (c) at least one of the flanks (16a, 16b) of the slot (12) forms a linear conical form with an opening angle (); (d) in relation to the height (Hs) of the clamp ring (6), the height (HN) of the base surface (14) of the slot (12) is in the region of 15% to +15%, that is, 0.85HN/HS1.15; (e) the inner surface (6a) of the clamp ring (6) extends parallel relative to the base surface (14) of the slot (12) which is arranged in the connecting part (8, 10); (f) in the clamped state, the inner radius of the clamp ring (6) is smaller than or equal to at least one of the radii of the slot upper edges; (g) the sleeve rolling-lobe flexible member (4) is not compressed in the region between the base surface of the slot (12) and the inner side (6a) of the clamp ring (6); (h) the clamp ring (6), with at least one slot flank (16a and/or 16b), forms a constriction which clamps the flexible member wall of the end section (4a and/or 4b). Since the inventive drop base ring clamping of sleeve rolling-lobe flexible members can be subjected to heavy loads and is extremely reliable, it can be used, preferably, for utility vehicles (trucks and buses).
The invention relates to a rolling-lobe air spring and especially the attachment of a rolling-lobe flexible member to a connecting part (air spring cover and/or roll-off piston). The connecting part is to be applied pressure tight at the ends to the flexible member with each end being form tight and pull tight.
European patent application 0 319 448 A2 is directed to the end attachment of an air spring flexible member to respective connecting parts. FIG. 4 shows all essential details. The attachment part includes a slot for attaching a sleeve rolling-lobe flexible member end section. This slot has a base surface which can be provided with peripherally-extending grooves 24. The flanks of the slot are partially curved and partially conically inclined at different angles and . The clamping takes place via the compression of the flexible member over the entire elevation of the clamp ring. The elastomeric material of the flexible member is practically incompressible. For this reason, the clamping over the entire clamp ring elevation hR has the consequence that, to a considerable extent, elastomeric material is squeezed out at both sides of the clamp ring in the longitudinal direction of the flexible member. In view of the fact that the flexible member is provided with a reinforcement, which is expandable slightly compared to the rubber, the problem is present that the considerable longitudinal displacement of the elastomeric material can lead to unwanted excessive longitudinal stresses within the flexible member and therefore to a possible separation of the elastomeric material from the reinforcement which can expand only slightly.
In order to avoid internal longitudinal stresses of the above kind in the clamping region of the flexible member, DE 41 42 561 A1 suggests that the end section of the flexible member not be pressed over the entire elevation of the clamp ring and instead only at an upper and/or lower constriction in the region of at least one of the flanks of the attachment slot. FIG. 4 shows the constriction 21 at the lower slot flank 22 while the flexible member is practically not compressed over the entire clamping elevation of the clamp ring. Because of the rectangular slot cross section in the construction shown in FIG. 4, the insertion of the clamp ring, which is to be mounted, is not easily possible.
An easier assembly possibility is to be expected by the variation shown in FIG. 1. Here too, the basic idea of the flexible member attachment is that no compression is present over the elevation of the clamping length and therefore no greater material displacement is present in the longitudinal direction of the flexible member; instead, the basic idea of the flexible member attachment is rather that the clamping takes place only at short constrictions 21 in the region of the slot flanks. The rounded clamp geometry includes no gripping capacity. Accordingly, with respect to the construction shown in FIG. 1, the desired pull-out strength does not appear to be satisfied especially to the extent as is required in commercial vehicles.
The task of the present invention is therefore a reliable attachment of a sleeve rolling-lobe flexible member to a connecting part. A longitudinal displacement of elastomeric material relative to the reinforcement, which is integrated therein, is substantially avoided.
According to claim 1, the solution of this task is especially a configuration of at least one clamp constriction which is, on the one hand, more effective and, on the other hand, easier to assemble.
The plastically deformable clamp ring is radially pressed. Because of the conical configuration of the slot flanks, a self-adjusting clamping of the sleeve rolling-lobe flexible member end regions disposed in each case between the slot and the clamp ring results. The section of the sleeve rolling-lobe flexible member end region, which is disposed between the clamp ring inner surface and the base of the slot, is only minimally clamped, that is, it is only minimally pressed by the amount which the incompressibility of the wall of the flexible member permits.
The sleeve rolling-lobe flexible member is, as a practical matter, not pressed over the entire clamp ring elevation which corresponds approximately to the elevation of the base of the slot and this has the consequence that no material is displaced in the longitudinal direction of the sleeve rolling-lobe flexible member. A separation of the reinforcement, which is integrated in the elastomeric material of the flexible member, is therefore not to be feared. A clamping is only pointwise, namely, at an upper constriction and a lower constriction. The clamping realized here is so effective because a linear surface (slot flank) and a wedge-shaped edge (of the clamp ring) lie opposite each other as clamp jaws. Because of the shortness of the constriction, there is no significant longitudinal displacement of the elastomeric material. Here too, a separation of the elastomeric material from the reinforcement is not to be feared. The reinforcement is integrated into the sleeve rolling-lobe flexible member.
A one-end drop-base contour (FIG. 7) is sufficient to hold the flexible member for clamping where the load is not too great.
The flexible member is compressed at the clamp point to approximately 45% to 65% of its thickness because of the geometric relationships (slot base elevationclamp ring elevation and opening angle () between perpendicular and flank direction =25 to 35) (for simple conical flanks) or 2=50 to 70 (in the event that both flanks are conically inclined).
To satisfy higher sealing requirements and in order to achieve a further increase of the tear out strength, it can be purposeful to provide the drop base with a circular profile (multi-tooth surface, FIG. 5, or a slotted surface, FIG. 6). In this way, there results an air spring clamping which can be overall subjected to greater load.
If the inner edges of the clamp ring are slightly rounded or the inner edges are provided with a bevel, then a tearing through of the flexible member at the clamping point is reliably avoided.
The configuration according to the invention of the drop base clamping is also suitable without difficulty for so-called folded-over sleeve rolling-lobe flexible members or sleeve rolling-lobe flexible member ends.
The drop base clamping of the sleeve rolling-lobe flexible member according to the invention can be intensely loaded and is most reliable. For this reason, the drop base clamping can preferably be used for commercial vehicles (trucks and busses).
Overall, sleeve rolling-lobe flexible member air springs having the drop base clamping according to the invention define a cost effective alternative to rolling-lobe flexible member air springs having ring-reinforced beads on conical sealing surfaces of the attachment parts.
The air springs 2 shown in FIGS. 1 and 2 comprise essentially a sleeve rolling-lobe flexible member 4 having end sections (4a, 4b) which are applied form tight, pull tight and pressure tight to respective connecting parts (8, 10). The upper connecting part 8 is, in each case, an air spring cover while the lower connecting part 10 is, in each case, a roll-off piston. Each of the connecting parts (8, 10) has a specially formed slot 12 for attaching corresponding ends (4a, 4b) of the sleeve rolling-lobe flexible member. End section 4a or 4b of a sleeve rolling-lobe member 4 is placed in corresponding slots 12 and clamped with the aid of a corresponding clamp ring 6. Because of the plastic deformation of the clamp ring 6, the sleeve rolling-lobe flexible member 4 is pressed into the slot 12 which extends peripherally around each connecting part 8 and/or 10 and is configured as a drop-base contour.
The air spring 2 shown in FIG. 2 distinguishes from the air spring 2 of FIG. 1 in that here the sleeve rolling-lobe flexible member 4 has first been folded over for the purpose of attachment at the roll-off piston 10. In this way, the outer side of the corresponding sleeve rolling-lobe flexible member end 4b comes to rest at the contact surface of the slot 12 of the roll-off piston 10; whereas, the inner side of the end 4b of the sleeve rolling-lobe flexible member comes in contact against the inner side of the clamp ring 6.
The advantage of the attachment of a sleeve rolling-lobe flexible member 4 or sleeve rolling-lobe flexible member end 4a or 4b, which has been folded over in advance, is that a deflection is possible without difficulty also in the completely pressureless state of the air spring 2. A buckling and therefore damage of the sleeve rolling-lobe flexible member 4 is reliably avoided.
FIG. 3 shows details of the slot 12 disposed in the connecting part (8, 10) (cover 8 and/or roll-off piston 10). The slot 12 has a cross section shaped as a truncated cone having a straight line base 14 of elevation HN and linearly beveled side flanks (16a, 16b). The two side flanks (16a, 16b) are each inclined at an angle relative to the perpendicular L so that the slot 12 is wider at its opening than at its base 14. The depth of the slot 12 is identified by T.
As shown in FIG. 4, the depth T of the slot 12 is greater than the thickness S of the sleeve rolling-lobe flexible member 4. In this way, the inner side of the clamp ring 6 comes to lie below the upper edges of the slot flanks (16a, 16b). The spacing from the bottom 14 of the drop base to the clamp ring 6 corresponds approximately to the wall thickness S of the sleeve rolling-lobe flexible member 4. The clamp ring 6 is provided with bevels (0.545) at its peripheral edges in order to avoid damage to the wall of the flexible member. The depth of the slot 12 should be approximately (flexible member wall thickness+ clamp ring width B) in order to avoid a pull-off of the clamp ring 6. The reduction of the flexible member wall thickness S in the region of the clamp ring edges can be varied by the press-in depth and elevation of the clamp ring 6 as well as a variation of the flank angle of the drop-base contour 12. Depending upon the configuration of the flexible member wall and the requirements on the clamping, the optimal flexible member wall thickness reduction can lie at 30% to 75% of the wall thickness S of the flexible member.
In addition, FIG. 4 shows that the clamp ring elevation HS corresponds approximately to elevation HN of the slot base 14.
From the geometric relationships shown, the clamping according to the invention has two constrictions, namely, between the upper and lower inner edges of the clamp ring 6 on the one hand and the respective flanks 16a and 16b of the slot 10 on the other hand. In this way, a point compression of the flexible member 4 is approximately 50% of its thickness S.
(A two point compression can be seen only in the cross-sectional view. Actually, a two-fold circular compression takes place along the inner upper edge and the inner lower edge of the circularly-shaped clamp ring 6.)
FIGS. 5 to 7 show specific embodiments of the sleeve rolling-lobe flexible member clamping. According to FIG. 5, the slot base 14 has risers (18a, 18b, . . . ) which are peripherally arranged on the cylindrical slot surface.
According to FIG. 6, peripherally-extending recesses (20a, 20b, . . . ) are provided on the slot base 14.
FIG. 7 shows a one-sided clamping of a sleeve rolling-lobe flexible member end (4a or 4b); that is, the slot flank beveling provided by the invention is configured only at a single slot flank 16a whereas the other slot flank 16b is at right angles and does not contribute to clamping the sleeve rolling-lobe flexible member end 4a or 4b.