US 3749389 A
Leaf spring having at least one lead and a fastening clip in the centre part of the leaf or leaves. A corrugation extending throughout the width of the leaf or leaves adjoins two corrugations in the clip on each side of the leaf or assembled leaves.
Description (OCR text may contain errors)
EJ165160 iafis mm 1 Dunehemin 1 1 July 31, 1973 LEAF SPRING HAVING AN HMPROVED  References Cited FASTENHNG UNITED STATES PATENTS lnventofl Michel Dlmlwmifl, 3,190,632 6/1965 Barenyi 267/52 Lambres-les-Douai, France 3,080,161 3/1963 Felbum Assign: messons D No"! Douai, 3,l97,l90 7/1965 Mlyashlro 267/52 France Primary Examiner-James B. Marbert  plied: July 1971 AttorneyBums, Doane, Swecker & Mathis ] App]. No.: 167,289
 ABSTRACT  Foreign Application Priority Data Leaf spring having at least one lead and a fastening clip Aug. 4, 1970 France 7028761 in the centre part of the leaf or leaves. A corrugation extending throughout the width of the leaf or leaves ad-  US. Cl. 267/52 joins twocorrugations in the clip on each side of the  Int. Cl. F161 l/22 leaf or assembled leaves.  Field of Search 267/52 4 Claims, 6 Drawing Figures The present invention relates to vehicule suspension leaf springs comprising at least one leaf and interposed between the suspended part and the unsuspended part of the vehicule.
In such springs, it is known that the leaves are surrounded in their centre part by a forged cage termed a clip and are centered with respect to each other and with respect to the clip by bolts or indentations. When bolts are used as centering means, it is necessary to provide apertures in the leaves and this of course results in a reduction in the section of each leaf and consequently weakens the spring. To a less extent the use of indentations also results in a discontinuity which weakens the leaves concerned. It is then necessary, in order to obtain sufficient strength in the centre part of this spring, to embed it in a long clip which reduces the flexibility.
The advantages afforded by a preforming of the spring are known as concerns the increase in the allowable load and above all the life of the spring. This operation is carried out in the cold state by applying to the spring an overload so as to exceed the elastic limit of the metal and produce plastic deformations. In order that this operation be effective, the whole of the useful part of the spring must be subjected to this load exceeding the elastic limit. Now, the clip of the spring is never perfectly rigid and the spring is not completely embedded therein, above all now that it is desired to render,
such assemblies lighter and consequently employ short clips having lowv rigidity, and is therefore necessary to produce also a preforming in the region inside the clip.
When the leavesare provided with ,apertures for the passage of bolts or are deformed by thepresence of indentations, when the preforming operation is carried out, the elastic limit is reached sooner in the section in which the aperture or, indentation is located than:in other parts of the spring. Consequently, the springis deformed plastically in this centre region whereas, the remainder of the spring hardly reaches the elastic limit and undergoes practically no plastic deformation. It is practically impossible to increase the preforming force otherwise there is a danger. of initiatinga split or crack in the section weakened by an apertur'e or indentation. Thissplitting being moreover encouraged by the sudden change in'section.
An object of the invention is to provide a centering and fastening device for a leaf spring which does not reduce the section of the spring or result in sudden variations which permits the utilization of relatively short clips .and which also permits the submission of the spring to a preforming operation over its entire length so as to ensure a substantially prolonged spring life.
The invention provides a leaf spring comprising at least one leaf and a detachable fixing clip disposed in the centre part of the spring, wherein the or each leaf has in its fastened or clipped centre part acorrugation extending throughout its width, the clip having on each side of the springtwo faces having corrugated portions of corresponding'shape.
In view of the fact that'these corrugations extend throughout the width of the or each leaf, any discontinuity in the section and any preferential fractureregion is avoided. I
Further features and advantages of the invention will .be apparent from the ensuing description with reference to the accompanying drawing.
, parallel to the plane of the leaves.-'
In the drawing:
FIG. 1 is a longitudinal sectional view of a first embodiment of'a leaf spring according to the invention FIG. 2 is a sectional view taken along line 2-2 of FIG. 1
FIGS. 3 and 5 are views similar to FIG. 2 of modifications, and
FIGS. 4 and 6 are sectional views taken along lines 4-4 and 66 of FIGS. 3 and 5.
FIGS. 1 and 2 show a spring R, comprising respec-' tively a single leaf 1 which has at its ends fixing eyes 2 and is integral in its centre portion with a fastening clip 3. The leaf 1 has in the centre portion a corrugation la whose concavity is upwardly facing in the presently described embodiment, that is, it has the same orientation as the whole of the spring. The clip 3 is composed of two parts 4 and 5 having a U-shaped section (FIG. 2), these two parts 4 and 5 having in the web portion thereof 4a, 5a, a corrugation corresponding to the corrugation la of the leaf and being provided in their flanges 4b, 5b, with apertures'4c, 50, for the passage of suitable fixing means.
In the embodiment shown in FIGS. 3 and 4, the illustrated spring R, has two leaves ll, 12, which are corrugated in their centre part and the fastening clip 13 is constructed in a somewhat different way. This clip 13 is inone piece anddefines two corrugated strips 13a, 13b, which are disposed on each sideof the leaves and flanges 15a, 15b, which extend in a direction perpendicular to the leaves and are provided with openings 16 for the passageof fixing means. s-
The spring R shown-in FIGS. Sand 6 also has two" leaves 21,22, which are corrugated in their centre part andthe fastening clip 23 is soconstructed as-to permita different fixing method, two fixing tabs 24a, 24b extending fromthe upper strip of the clip in a direction It will be understood tha't-thesevarious modifica- I tions, which concern-the number of leaves of whichthespring may be ,composed,.the particular construction .of the clips and especially the. position of the means for. fixing it on an axle or other part of a vehicule, are .not
critical and may be subjected to various other modifications. The essential feature of the invention in all these embodiments resides-in the. fact that the centering of the leaveswith respect'to each other and with respect to the clip is achieved by forming in the leaves and in the adjacent strips of the clip corrugations which extend throughout the width of the leaves and therefore do not constitute a region of reduced section which would weakenthe spring. The utilization ofsuch centering means enables relatively short clips to be employed so that maximum resiliency of the spring is achieved. Owing to this arrangement, it isalso possible to impart to the spring a prefonnation whichis roughly thesame'throughout its length and thereby substantially prolong its life.-It has beenfound that it ispossible to increase this preforming load by 30 50 percent without danger, which increases the-elastic limit ofthe spring correspondingly. Specific trials have shownlthat, for a given load, the life of a spring accordingtothe invention, measured by the number of-o'scillation cycles before fracture under given bending conditions, was of the order of 300,000 -'500,000 cycles whereasusually the life of a conventional spring is of the order to 100,000 cycles. This clearly reveals the importance of the improvement both from the viewpoint of perfor mance and reliability and the viewpoint of cost.
Having now described my invention what I claim and desire to secure by Letters Patent is l. A leaf spring structure comprising at least one leaf, a corrugation extending throughout the width of the leaf in 'a centre part the latter thelatter and a detachable fastening clip disposed in a centre part of the spring, said clip comprising two flanges which extend each in one side of said spring in a direction perpendicular to the plane of the leaf, two bearing surfaces extending from one flange to the other and each adjoining one opposite face of said spring, fixing tabs fast to said flanges, means defining apertures in these tabs for the passage of fixing means and corrugations in each of said bearing surfaces, said corrugations having a shape corresponding to the corrugation of the leaf.
2. A leaf spring structure as claimed in claim 1, wherein the clip comprises two members one inside the other, each member having twofianges and a web portion interconnecting the flanges and defining a U- shaped cross section, bearing surfaces on said two web portion adjoining opposite faces of the spring and being corrugated, the flanges of outer member extending beyond the inside member and forming two first fixing tabs and the flange of inside member forming two second fixing tabs parallel to the first, one on each side of the spring, and means defining apertures in said tabs for the passage of fixing means.
3. A leaf spring structure as claimed in claim 1, wherein the clip is in one piece and has two corrugated strip portions disposed on each side of the leaf and two flanges which extend in a direction perpendicular to the plane of the leaf and have apertures for the passage of fixing means.
4. A leaf spring as claimed in claim 1, wherein the clip comprises two fixing tabs whiehextend from an upper part of the clip in a direction parallel to the plane of the leaf.
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