LEAF SPRING AND LEAF THEREFOR

Abstract: A multi-leaf leaf spring comprises a first leaf (157) which bends when the spring is subjected to a load up to a pre­ determined value, and a second leaf (101) which bends with the first leaf when the load exceeds the predetermined value. The second leaf comprises a longitudinal extending beam composed of 40-75% by volume of filaments (510) at least 80% of which are aligned longitudinally along the beam and under tensile stress, the remainder of the beam being composed of a matrix of plastics material which binds the filaments together.

Description: EUROFEAN PATENT SPECIFICATION TITLE LEAF SPRINGAND IEAF THEREFOR IJESCRIPHON "lEAP SPRING SD THEREFOR" This invention relates to leaf springs and leaves therefor. Multileaf vehiclar springs are disclosed in, for example, U.S. Patent Specifications Nos. 2,052,062; 3,292,918 and 3,493,222. Moreover, springs comprising leaves which contain filamentary solids in an organic solid are disclosed in for example U.S. Patents 2,600,843; 2,829,881 and 3,142,598. According to the present invention there is provided a spring leaf comprising a longitudinally extending beam composed of from about 40 to about 75% composedby volume of filaments, the remainder comprising a continuous organic solid plastics material that binds together said filaments,sbout or more by weight of said filaments being packed substantially uniformly throughout said organic solid, extending along the beam and being under tensile stress. In a preferred embodiment of the invention, the leaf comprises a beam with about 40-75% (preferably about 50-6046) by volume filamentary solids and a remainder fraction (preferably about 60-2 0, more preferably about 50- 4 by volume) of continuous organic solid. The organic solid binds together the filamentary solids. At least about 80% (more preferably, at least about 9#) by weight of the filamentary solids comprises a multitude of discrete, tensilely stressed, filamentary solids, densely packed substantially uniformly throughout the organic solid. These discrete, tensilely stressed and densely packed, filamentary solids coextend the beam longitudinally in a plurality of planes that accept tensile or compressive stress, respectively, upon a flexure of the spring that bends the beam. In preferred embodiments, the beam has between about 50-6 % by volume glass fibre and more preferably more glass than organic solid by volume. Up to about 10% by weight of the filamentary solids comprises randomly oriented filamentary solids in a mat on a surface of the beam that receives lòngitudinal compressive stress. Up to about 1$ by weight of the filamentary solids comprise woven filamentary solids that have fibres oriented across one another substantially in a plane of the a#f#orementioned planes. In certain embodiments, the beam has a configuration that is substantially straight along a longitudinal axis without the aforementioned flexure. The beam has a cross-section that is preferably substantially rectilinear. In an especially preferred embodiment, this invention relates to a multirate, multileaf vehicular spring. In such spring, a first leaf (normally a set of leaves comprising a first leaf) acts independently of a second leaf under a first load; but it acts together with the second leaf under a second load which is greater than the first load. The first leaf has ends adaptable to attach the spring to a vehicle at first and second vehicle locations. The second leaf has a centre section bindable with a centre section of the first leaf to the vehicle at a third vehicle location. The third vehicle location is between the first and second vehicle locations. The improvement of the invention with respect to such a multirate spring comprises a second leaf that is a light weight leaf. The light weight leaf comprises a beam, preferably straight, that has about 40-7# % (preferably about 50-6 %) by volume filamentary solids of a first modulus. A remainder fraction (preferably about 60-2#, more preferably about 50 4 by volume) comprises continuous organic solid of a second, lower modulus. The organic solid (e.g., vinylester or polyester or epoxy thermoset resin) binds together the filamentary solids. At least about W (preferably at least about 90%) by weight of the filamentary solids comprise a multitude of discrete, tensilely stressed filamentary solids, densely packed substantially uniformly throughout the organic solid. These discrete, densely packed and tensilely stressed, filamentary solids coextend the beam longitudinally in a plurality of planes that accept tensile or compressive stress, respectively, upon a flexure of the spring that bends the beam. The beam in these especially preferred embodiments is preferably substantially straight under the sforementioned first load. The beam preferably has a configuration that has a substantially rectilinear cross section. The beam also has a preferred glass content as well as random and woven filamentary solids as noted hereinabove. Embodiments of the invention will now be described, by wRy of example only with reference to the drawings, in which: Figure 1 illustrates schematically the operation of a multirate spring in accordance with this invention. Configurations I, II, and III denote spring conditions, somewhat exaggerated for purposes of illustration, under increasingly larger loads. Figure 2 illustrates graphically spring rates for a multirate spring. The ordinate is load in newtons; the absissa is spring height in millimeters. Figure 3 illustrates a multirate spring in accordance with this invention. Figure 4 illustrates a cross-section through the spring of Figure 3 along line II-II of Figure 3. Figure 5 illustrates a cross-!section through the spring of Figure 3 along line from III-III of Figure 3. Figure 6 is a side view of a spring seat upon which a spring such as in Figure 3 may be mounted. Figure 7 is an end view of the spring seat of Figure 6. Figure 8 is a view of the spring seat of Figure 6 from below. Figure 9 is a schematic cross-section of a spring leaf. in accordance with the invention as incorporated in the spring of Figure 4 and illustrating its composition. Figure 1 of the drawings schematically illustrates amultifleaf, multirate composite leaf spring 150. The leaf spring 150 has a main leaf 156 and two secondary leaves 152 and 154. The composition of the main and secondary leaves 152, 154 and 156 is steel. The leaf spring 150 additionally incorporates a leaf 100, composed of glass fibres in a eolid-matrix of thermosetting organic plastics material formed into a straight flat beam. Configuration I of Figure 1 sh#s the leaf spring 150 under a low load. The spring 150 conforms to configuration I, when for example, a vehicle carrying it is unloaded, e.g., "curb position". It will be observed that the main and secondary leaves 156, 152 and 154 are bent, whilst the additional leaf 100 remains undeflected. Configuration III of Figure 1 shows the leaf spring 150 under a high load. The spring 150 conforms to configuration III, when, for example, a vehicle carrying has a capacity load, i.e., "normal load". In this condition all the leaves of the leaf spring 150 are bent. The rating of the spring is therefore higher in this configuration than in configuration I. Configuration II of Figure 1 shows the leaf spring 150 under a load intermediate between the first and second loads at which the additional leaf 100 is just about to be bent by the load.- Figure 2 approximates graphically the variation of the deflection of a leaf spring (x axis in mm.) with applied load (y axis in newtons). The deflection measurement corresponds to the overall height of the leaf spring 150. The measurements were made on the leaf spring 250 illustrated in Figure 3, the leaf #spring being unclam#ped and mounted on rollers during the meansurements. The slope of line 200 corresponds to the rating of the leaf spring when it is in configuration corresponding to that shown at I in Figure 1. The slope of line 202 corresponds to the rating of leaf spring 250 when it is in a configuration corresponding to that shown at III of Figure 1. The intersection of lines 220 and 202 represents a transition between the spring rates which occurs when the leaf spring 250 is in a configuration corresponding to that shown at Ii in Figure 1. The point 201 indicates the conditions under which the main leaf of the spring 250 lies flat. This occurs at a lower load than the load at which the transition between the spring rates occurs because, unlike the leaf spring 150, the additional leaf 100 is spaced from the other leaves by a spacer 180. As seen in Figure 3, the leaf s#pring 250 has a set of steel leaves 153, 155 and 157; leaf 157 being the main leaf. These leaves give the leaf spring 250 the first spring rate. The additional leaf 101 comprises a beam of glass fibres in a matrix of a thermosetting plastics material. The additional leaf 101 in combination with the leaves 153, 155 and 157 produces the second spring rate. The main leaf 157 has mounting eyes 140 and 160 which comprise integral curvatures 162 and 142 at the ends of thenain leaf 157. Each eye 140 and 160 contains a press fitted bush 144 and 164, within which are mounted metal sleeves 146 and 166. In use, the leaf spring 250 is mounted on a vehicle through the sleeves 146 and 166 (a) to the chassis or body on either side of the axle or (b) to the axle at spaced locations One of the sleeves 146 and 166 is mounted to the vehicle for example by a shackle to accommodate relative movement of the ends of the leaf spring during flexing. A clip 170 holds the leaves 153, 155 and 157 together and towards one end of the spring 250 and prevents excessive splaying of leaves 153, 155 and 157. An additional clip (not shown) may also be provided at the opposite end portion of the leaf spring 250 if desired. In use the clip 170, is positioned forwardly of the amle Rowhich the spring 250 is attached, thus prevents entry of gravel or other particulate between the leaves 153, 155 and 157, particularly during acceleration of the vehicle. Fastening means l90 extends through the leaves 153, 155 157 and 101 and permits alignment of the leaf spring 250 in a spring seat 400 (Figures 6, 7 and 8). The fastening means 190 also extends through a spacer 180 (Fig.4)#and'' delays engagement of leaf 101 beyond flat main leaf" condition of main leaf 157. The spacer 180 may be composed of aluminum or of any other such formable material. As best seen in Figure 4, the fastening means 190 comprises a threaded bolt 192 having a cap 196 and a nut 194. The bolt 192 fits snugly in an orifice 198 through the main and secondary leaves 153, 155 and 157 and an orifice 102 through the additional leaf 101. The cap 196 fits into an orifice 408 in the spring seat 400. The spacer 180 (Figure 4) has integral creep resistors 182 that wrap around the additional leaf 101. The leaf 101 has curved edges 104 that fit snugly into the intersection of the spacer portion 184 and the creep resistance portions 182 of the spacer 180. The creep resistance portions 182 of the spacer 180 resist movement of the leaf 101 during flexing of the spring 250. Figure 5 shows a cross-section through the clip 170. A rivet 172 fits tightly into two orifices 172 and 174 of the clip 176 and the leaf 153, respectively to maintain engagement between the clip 176 and the leaf 153. Figures 6, 7 and 8 show side views and a bottom view (looking up from the axle) of the spring seat 400. The seat 400 comprises a top, flat portion 406 upon which the leaf spring 250 rides. The flat portion 406 has a width equal or slightly greater than the width of leaf 101 and a length of about two times its width. The seat 400 has an orifice 408 into which the bolt head 196 fits. a The spring seat 400 has/curved portion 402 which conforms to the axle housing (not shown) of the vehicle. The curved portion 402 is interrupted by nubs 420 which, during assembly of the spring 250 on to a vehicle, provide metal by means of which the seat 400 can be welded to the axle housing. The nubs 420, accordingly, disappear during the welding operation. The spring seat has an external curved section shown at 404 in Figures 6 and 7, which slope away from flat portion 406. The flat portion 406 thus forms a plateau upon which the leaf spring 250 rides, thereby providing a smooth engagement between the zoning leaf 101 and the seat 400. Figure 8 shows sections 410 and412 of members of U-bolt assemblies of conventional construction which wrap around the axle housing. They engage a single plate above the spring leaf 157. Figure 9 illustrates a cross-section through the spring leaf 101. The section is substantially rectangular with corners having a small radius. Leaf 101 comprises filamentary solids in 8 continuous organic solid. Sections 500, 502 and 510 of leaf 101 show the relative positions and character of the filamentary solids in the matrix of thermosetting p ] Etics material 504. Sections 500, 502 and 510 extend the length of leaf 101. The leaf 101 contains about ss by volume of filamentary solids which comprise glass fibres; the remainder of leaf 101 is a continuous organic solid plastics materisl(thermoset polyester resin) that binds the filamentary solids together. The leaf 101 of Figure 9 has been made by a pultrusion process. In the pultrusion process, pullers draw filaments coated with resin through a heated die. The resin hardens in the die. Examples of pultrusion processes appear in U.S. Patents 4,154,634; 3,853,656; 3,793,108; 3,684,622; 3,674,601; 3,530,212; and 2,741,294 The leaf 101 of Figure 9 has three arrangements of filaments. Greater than about 95% by weight of the filamentary solids comprise a multitude of discrete, tensilely stressed, filaments densely packed substantially uniformly throughout thermoset polyester 504. These filaments extend along leaf 101 in a plurality of planes which receive tensile or compressive stress upon flexure of multirate spring 250 sufficient to bend the spring leaf 101. The sections through a portion of such filaments appear as 510 in Figure 9. (The sections 510 are slightly enlarged relative to the remainder of leaf 101, and the sections of other of the filaments, substantially uniformly dispersed throughout leaf 101, have been omitted from Figure 9 for clarity). Less than about 2 by weight of the filaments in the spring leaf 101 are randomly oriented. The portion 502 in Figure 9 shows the position of these randomly oriented filamentary solids in the spring leaf 101. The randomly oriented solids form a mat (e.g. glass fibre mat) in one surface of the leaf 101. The mat side of leaf 101 rests on spring seat 400 in multirate spring 250 of Figure 3. (The size of the portion 502 is exaggerated for the purpose of illustration, the mat being actually only a few tlass fibres thicks. Less than about $ by weight of the filamentary solids in leaf 101 comprise a woven mat of filamentary solids which is held tightly within the longitudinally extending filamentary solids. Portions 500 of Figure 9 illustrate positions of the woven mat in leaf 101. The woven mat has filamentary solids positioned across one another and therefore contains fibres that are traverse to the longitudinal dimension of the spring leaf 101. These traverse fibres reduce creep of leaf 101. (The portions 500 exaggerate for purposes of illustration the relative volume taken by the woven mats. Each woven mat in the lea¯ 101 is compressed such that it has a volume that is from 1 to 10 fibres thick in a cross-section of leaf 101). In an alternative embodiment of the invention the spacer creep resistors 182 shown in Figure 4 are omitted. In this embodiment leaf 101 and leaves 153, 155 and 157 have equal widths. In still other embodiments, leaf 101 is as above described with respect to continuous and filamentary solids, but, when unloaded, is curved. In a multirate spring embodiment, such a curved leaf may engage leaves 153, 155 and 157 before or after the main leaf has been deflected into a flat position depending, for example, on whether leaf 101 has a positive or negative curvature with respect to leaf 157. In still other embodiments, such a curved spring leaf may be included in the main and secondary leaves.

Claims: CLAIMS 1. A spring leaf comprising a longitudinally extending beam composed of from about 40 to about 75 by volume of filaments, the remainder comprising a continuous organic solid plastics material that binds together said filaments, about 80% or more by weight of said filaments being packed substantially uniformly throughout said organic solid, extending along the beam and being under tensile stress. 2. A spring leaf in accordance with Claim 1, wherein the filaments constitute from 50 to 60ack by volume of the beam. 3. A spring leaf in accordance with Claim 1 or Claim 2, wherein said beam is made by drawing the filaments and the plastics material through a die. 4. A spring in accordance with any one of Claims 1 to 3, wherein said organic solid plastics material comprises a polyester or a vinyl thermosetting resin. 5. A spring leaf in accordance with any one of Claims 1 to 4, wherein up to about 10% by weight of the filaments are randomly oriented in a mat on a surface of said beam. 6. A spring leaf in accordance with any one of Claims 1 to 5, wherein up to about 16 by weight of the filaments are oriented across one another in a longitudinal plane of said beam. 7. A spring leaf in accordance with any one of Claims 1 to 6, wherein said beam is substantially straight when it is not subjected to bending loads. 8. A spring leaf in accordance with any one Or Claims 1 to 7, wherein said beam has a substantially rectangular cross section. 9. A spring leaf in accordance with any one of Claims I to 8 wherein the filaments are of glass. 10. A leaf spring comprising a first spring leaf which bends under a load up to a predetermined value, and a spring leaf according to any one of the preceding Claims connected to the first spring leaf to bend with the first spring leaf when loads greater than the predetermined value are applied to the spring.

Inventors: FESKO, DONALD GEORGE, GALANIUK, ALEXANDER H.
Applicants: FORD FRANCE SOCIETE ANONYME, FORD MOTOR COMPANY, FORD MOTOR COMPANY LIMITED, FORD-WERKE AKTIENGESELLSCHAFT
Application year: 1981
Main classification: F16F1
IPC codes: F16F1, B60G11, B29C70