GB2049875A

GB2049875A - Improvement in or relating to leaf springs

Info

Publication number: GB2049875A
Application number: GB8009379A
Authority: GB
Original assignee: Stahlwerke Brueninghaus GmbH
Current assignee: Stahlwerke Brueninghaus GmbH
Priority date: 1979-03-31
Filing date: 1980-03-20
Publication date: 1980-12-31
Also published as: GB2049875B; DE2912932C2; DE2912932A1; ES490066A0; ES8100831A1; FR2453321A1; FR2453321B1

Abstract

A leaf spring, especially a parabolic spring, comprises several spring leaves (10 to 13), which are held together and braced in an axle support region by clamping means and which are centred relative to one another by cooperating recesses and protrusions in the region of the clamping means. The clamping length (16) of the leaves (10 to 13) is smaller than the clamping means length (24) in the length direction of the spring. <IMAGE>

Description

SPECIFICATION Improvements in or relating to leaf springs The present invention relates to leaf springs, especially parabolic springs.

These are known springs with spring leaves which are held together and braced in the axle support regions by a spring shackle and which are centred relative to one another by recesses and protrusions arranged in the region of the spring shackle. In such a leaf spring, which for example is used in a rail vehicle, the spring shackle serves for mounting, fixing and bracing the spring leaves.

Wrought spring shackles are already known, such shackles being mounted on a stack of spring leaves in the cold state and wedged together with the leaves. A compensating plate is inserted between a main spring leaf and a wedge in order to protect the leaf against damage to its surface and to compensate for gaps due to manufacturing and assembly tolerances. To keep the individual spring leaves at a spacing and to protect the notch-sensitive tension sides against pressure points and corrosion, tinned intermediate plates, of soft sheet metal and slightly pointed at their ends, are generally placed between the leaves in the clamping region. The spring leaves, the compensating plate and the intermediate plate in the clamping region each have a prismatic region which is as long as or longer than the spring shackle length in the length direction of the spring.

This manner of clamping has the disadvantage that frictional movements between the spring leaves, between the leaves and the adjacent edges of the shackle and between the leaves and the intermediate plate or compensating plate occur at the shackle rims on springing in and out, because as dynamic tests have shown, such a clamping method does not provide sufficient rigidity to prevent co-springing of the central region of the leaf spring at the zones of the edges of the shackle. Due to the relative movement of the contact surfaces, wear due to friction takes place at the clamping edges, which can lead to notching effects, fatigue fractures and finally to spring breakage.

Spherical recesses and protrusions, so-called warts, are arranged in the centre of the clamping region of known springs for centering of the leaves. However, these do not provide an exact centring. The flatter the recess or protrusion, the more inexact the centring. An inexact centring has the disadvantage that relative displacement of adjacent leaves is possible in assembly of the shackle. As a consequence, the central regions, in which the leaves are in metallic contact, in part project appreciably beyond the edges of the spring shackle, which promotes wear due to friction and thus the risk of breakage.

There is accordingly a need for a method of clamping together spring leaves to provide greater security against breakage. For this purpose, exact centring of the leaves relative to each other is also required.

According to the present invention there is provided a leaf spring comprising a plurality of spring leaves located relative to each other by interengaged projections and recesses in a clamping zone of the leaves and clamping means so clamping the leaves together in,the clamping zone that the length of the clamped portions of the leaves is less than the length of the clamping means in the longitudinal direction of the leaves.

In a leaf spring embodying the invention, the ends of the clamping zone are within the clamping means, where the bracing of the leaf packet is fully effective and where the springing of the leaves is consequently inhibited so that relative movement and thus wear due to friction is prevented at the contact surfaces.

It is advantageous if intermediate plate elements, which determine the length of the clamping zone and the effective length of which is smaller than said length of the clamping means, are arranged in the region of the clamping means between adjacent leaves and/or between the leaves and the clamping means.

Advantageously, the leaves have parallel contact surfaces, the length of which determines the length of the clamping zone and is smaller in the region of the clamping means than said length thereof.

To provide the best possible centring of the leaves relative to each other and thereby exact maintenance of the desired length of the clamping zone, the recesses and projections preferably each have a cylindrical region, the projection of a spring leaf or of the clamping means being engaged in a corresponding recess of an adjacent spring leaf or in a recess in the clamping means, as the case may be.

In order that the tension sides of the leaves are not weakened, the projections thereof are preferably arranged on sides of the leaves intended to be stressed in tension and the recesses on the sides intended to be stressed in compression.

Embodiments of the present invention will now be more particularly described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal section of a leaf spring, in a clamping zone thereof, according to a first embodiment of the invention, Fig. 2 is a transverse section of the spring of Fig. 1, Fig. 3 is a longitudinal section of a leaf spring, in a clamping zone thereof, according to a second embodiment of the invention, Fig. 4 is a transverse section of the spring of Fig. 3, Fig. 5 is a longitudinal section of a leaf spring in a clamping zone thereof, according to a third embodiment of the invention, and Fig. 6 is a transverse section of the spring of Fig. 5.

Referring now to the drawings, there is shown in Figs. 1 and 2 a leaf spring which consists of a main spring body with main spring leaves 10, 11 and 12 and an additional spring leaf 13. All of the spring leaves are held together in the central region thereof by a spring shackle 14. The shackle 14 is drawn cold onto the completely assembled spring leaf packet.

Arranged between adjacent leaves are intermediate plates 15, the prismatic length of which in the length direction of the spring determines length 1 6 of the clamped portions of the leaves 11, 12 and 13 in the region of the shackle 14.

A compensating plate 17 for compensation for dimensional tolerances is included in the clamping zone of the spring leaves in the region of the shackle 14. The prismatic length of the compensating plate 1 7 in the length direction of the spring determines the length of the clamped portion of the main leaf 10. The clamping length 1 6 of all of the leaves 10 and 13 is smaller than the length 24 of the shackle.

Bracing of the leaves 10,11,12 and 13 in the shackle 14 is provided by a fixed wedge 18 and a driving wedge 1 9. The fixed wedge 18 has two lugs which bear against two outer edges of the shackle 14 when the fixed wedge 1 8 rests on the compensating plate 17. The bracing is effected by driving the wedge 19 into the shackle 1 from the side of the lugs 20. The wedge 19 is provided at its upper side with a bevel 21, which facilitates movement in the shackle 14 in the region of the rounded-off upper longitudinal edges of the shackle. After driving-in of the wedge 19, it is secured by a weld 22 in its position relative to the shackle 14.

The shackle 14 is centred on a vehicle axle with the aid of a spigot 23 disposed centrally at the underside of the shackle. The spigot 23 is provided with a cylindrical hole 25 into which engages a protrusion 26 of the leaf 13. The leaves 10, 11 add 12 are also provided with protrusions 26 at their undersides. The protrusions 26 are formed by formation of corresponding recesses 27 at the upper sides of the leaves in the centre of the clamping zone. A respective protrusion 26 engages in the recesses 27 and the protrusions 26 are cylindrical and closely interengage. In this manner, a very effective centring of the leaves 10, 11, 12 and 13 relative to each other and to the shackle 14 is provided, so that the contact surfaces of the leaves are disposed exactly centrally one above the other and only within the shackle 14.

The intermediate plates 1 5 are provided with round holes 34 so that they can be pushed over the protrusions 26. The compensating plate 1 7 also has a protrusion 28, by which it is centred in the recess 27 of the main spring leaf 10.

The further embodiments shown in Figs. 3 to 6 are in principle constructed the same as the leaf spring of Figs. 1 and 2. The recesses 27 are, however, disposed on the undersides, and the protrusions 26 on the upper sides, of the leaves 10 and 13. In this manner, the spring leaves are not weakened on their tension sides. These embodiments do not include intermediate plates, so that the clamping length 1 6 in this case is determined by the length of the parallel contact surfaces of the spring leaves in the region of the shackle 14.

In the embodiment of Figs. 3 and 4, the protrusion of the leaf 10 engages in a cylindrical hole 29 in an upper web 30 of the shackle 14. The spring leaf packet is thus centred at the upper side of the shackle 14. As a consequence, the compensating plate 17, fixed wedge 1 8 and driving wedge 1 9 are, for reasons of assembly, disposed at the underside of the shackle 14.

The embodiment shown in Figs. 5 and 6 has wedges arranged in the shackle 14 at the upper side of the spring leaf packet. Since the protrusion of the uppermost leaf 10 is directed upwardly, the wedge 18 is provided with a cylindrical hole 31 and the compensating plate 17 with a round hole 34, into which the protrusion 26 engages. This construction thus makes it possible to dispense with lugs for the retention of the wedge 1 8.

During driving-in of the wedge 19, the wedge 18 cannot be displaced relative to the spring leaf packet. The spring leaf packet is centred in the shackle 14 at the underside of the additional spring leaf 13 by means of a protrusion 32 which is formed on a lower web 33 of the shackle 14 and which is engaged in the recess 27 of the leaf 13.

Claims

1. A leaf spring comprising a plurality of spring leaves located relative to each other by interengaged projections and recesses in a clamping zone of the leaves and clamping means so clamping the leaves together in the clamping zone that the length of the clamped portions 6f the leaves is less than the length of the clamping means in the longitudinal direction of the leaves.

2. A leaf spring as claimed in claim 1, wherein a respective intermediate plate element is arranged between at least one pair of adjacent leaves, the length, in the longitudinal direction of the leaves, of the part of the plate element in contact with said pair of leaves being less than said length of the clamping means.

3. A leaf spring as claimed in either claim 1 or claim 2, wherein a respective intermediate plate element is arranged between the clamping means and an adjacent one of the leaves, the length, in the longitudinal direction of the leaves, of the part of the plate element in contact with the clamping means and said one of the leaves being less than said length of the clamping means.

4. A leaf spring as claimed in any one of the preceding claims, wherein at least one of the leaves is in direct contact in the clamping zone with an other one of the leaves, the length of the contacting surface portions of said leaves being less than said length of the clamping means.

5. A leaf spring as claimed in any one of the preceding claims, wherein the projections and recesses at least in part are substantially cylindrical in shape and each of the leaves is provided with a respective one of the projections and one of the recesses, the projection of each of the leaves being engaged in the recess of a respective other one of the leaves or in a corresponding recess in the clamping means.

6. A leaf spring as claimed in claim 5, wherein the clamping means is provided with a respective one of the projections, the projection of the clamping means being engaged in the recess of an adjacent one of the leaves.

7. A leaf spring as claimed in either claim 5 or claim 6, wherein the projection of each of the spring leaves is arranged on the side of that leaf intended to, in use of the spring, be stressed in tension and the recess on the opposite side of the loaf.

8. A leaf spring substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

9. A leaf spring substantially as hereinbefore described with reference to Figs. 3 and 4 of the accompanying drawings.

1 0. A leaf spring substantially as hereinbefore described with reference to Figs. 5 and 6 of the accompanying drawings.