LEAF SPRINGS OF COMPOSITE MATERIAL

Abstract: A leaf spring of composite, F.R.P, material with an attachment member e.g. a bush (12) lying in a recess (11) extending transversely of an end portion (10) of the spring, held therein by a clamping member (13) extending around the attachment member (12) and lying against surfaces of a spring part (16) adjacent the terminal position, wherein parts (14, 15) of the clamping member are held to the spring by a sheet metal element (17) extending transversely around the spring and deformed into engagement with recesses provided either in the parts (14, 15) of the clamping member or in separate elements (20, 21) thereon.

Description: Title: Leaf Springs of Composite Material. DESCRIPTION OF INVENTION This invention relates to leaf springs made of composite, fibre reinforced plastics, material. More particularly, the invention relates to an end fitting by which a composite leaf spring can be secured to a motor vehicle or other apparatus or equipment where it is to be used. It has been proposed, in our published European Patent Application 0070122, that an end fitting for a composite leaf spring can comprise an attachment member lying within a recess extending transversely of the spring at a- terminal portion thereof, and a clamping member extending around the attachment member and said terminal portion of the spring, and secured to the spring adjacent said terminal portion to hold the attachment member in the recess. The clamping member is of sheet metal, and has parts which extend along opposed surfaces of the spring adjacent the terminal portion thereof, spaced in the direction of bending of the spring. It is proposed in our European Patent Application aforesaid that the parts of the clamping member extending along the spaced surfaces of the spring adjacent its terminal portion can be secured by bolts or other fasteners passing through the spring, or by a strap extending transversely around the parts of the clamping member and spring. The strap may be welded eg spot welded, to the clamping member to secure it in position. Such methods have disadvantages. The provision of apertures in the spring to accept fasteners destroys the integrity of the fibres therein and hence may affect the characteristics of the spring. To weld in close proximity of the spring may damage it due to excessive temperatures being reached in the plastics component of the composite. It is the object of the present invention to provide an improved mode of securing the clamping member to the spring, which is effective in use, economical in manufacture and overcomes or reduces the above disadvantages . The present invention provides a composite leaf spring including, at an end thereof, an attachment member lying in a recess extending transversely of a terminal portion of the spring and held therein by a clamping member extending around said attachment member and terminal portion and having parts extending along spaced surfaces of the spring adjacent said terminal portion, characterised in that said clamping member is held to the spring by a sheet metal element extending transversely around said parts of the clamping member and deformed into engagement with recess means in or associated therewith. By the use of a sheet metal element or strap, deformed to hold the clamping member to the spring, the necessity of piercing the spring to accept fasteners is avoided. Also avoided is the possible damaging effect to the composite spring material of welding in close proximity thereto. The manufacturing operation of deforming the sheet metal element is readily performed using a relatively simple press, and is hence inexpensive. The recess means may be formed in the clamping member and may comprise an aperture in one or each respective part thereof. Alternatively, the recess means may be provided i a further element interposed between the sheet metal element and the or each respective part of the clamping element. Th latter expedient has the advantage that the spring itself i not likely to be damaged during- the operation of deformin the sheet metal element into the recess means. The arrangement may be such as to prevent the shee metal element from being bent in too tight radii at it corners. This eliminates the possibility of failure of th sheet metal elements from excessive deformation. These and other features of the invention will now b described by way of example with reference to th accompanying drawings, of which: Figure 1 is a side elevation of an end fitting of spring according to the invention; Figure 2 is an underneath view of the spring of Figur 1; Figure 3 is a section on the line 3-3 of Figure 1; Figure 4 is a section as Figure 3, but prior to deformation of the sheet metal strap. Figure 5 is a side elevation of a further embodiment of spring according to the invention; Figure 6 is an underneath view of the spring of Figure 5; Figure 7 is a section on the line 7-7 of Figure 5; Figures 8 and 9 are sections as Figure 7, showing further embodiments of the invention. Referring firstly to Figures 1, 2 and 3 of the drawings, there is shown an enα of a leaf spring of composite materia comprising fibres, e.g. glass fibres, set in a matrix of plastics resin material such as a suitable epoxy resin. terminal portion 10 of the spring defines a transversel extending recess 11 which accommodates an attachment membe in the form of a bush 12. The bush 12 may be the outer par of a well known metal-rubber-metal bush. The attachmen member is held in the recess 11 of the spring by a clampin member 13 which is of sheet metal, e.g. steel ana whic extends around the attachment member 12 and terminal portio 10. Parts 14, 15 of the clamping member lie against space surfaces of the part 16 of the spring adjacent the termina portion -thereof, which surfaces are spaced in the directio of bending of the spring in service. The attachment membe 12 may be welαeα, e.g. projection welαed, to the clampin member 13. The parts 14, 15 of the clamping member are helα to th spaceα surfaces of the spring 16 by a sheet metal element i the form of strap 17 extenαing transversely therearounα. T tighten the strap 17 so that the parts 14, 15 of the clampin member are securely held, a part 18 of the strap is αeforme into an aperture 19 proviαed in the part 15 of the clampin member. An aperture may also be provided in part 15 of th clamping member. The conαition of strap 17 prior to final assembly i shown in Figure 4. It is- relatively slack enabling it to b fitted over the parts 14, 15 of the clamping member when th latter is positioneα on the spring. A suitable pressin αevice can be useα to αeform the strap 17 into aperture 1 firmly to secure the clamping member ana attachment member t the spring. Referring now Figures 5, 6 ana 7 of the drawings, ther is here shown an e boαiment similar to that of Figures " 1 t 3, and like parts are given like reference numerals. In thi case, however, no aperture is provideα in the part 15 of th clamping member. Instead, further elements 20, 21 are inter posed between the strap 17 ana the parts 14, 15, ana thes elements aefine recesses or apertures into which the strap 1 is αeforme . The presence of complete apertures ensure location of strap 17 longituαinally of the spring. Th elements 20, 21 may be generally of U-shape, as shown i Figure 6 to define recesses, or may define complete aperture into which strap 17 is deformed. It will be appreciated tha it may be sufficient for only one element such as 20 or 21 t be provideα, with the strap 17 αefor eα in one position i this enables it to be tightened sufficiently. The use o elements 20, 21 spreads loaαs across the spring durin deformation of strap 17. Referring now to Figure 8 of the drawings, this shows a emboαiment in which edge portions 22, 23 of the parts 14, 1 of the clamping member are upturneα to define recesses int which the strap 17 is deformeα. The configuration o upturneα eαges 22, 23 is such that the bending of strap 17 a too sharp a radius is avoiαed. Further, it is ensured tha the strap 17 engages the sides of the spring to provid positive lateral location between the -clamping member an spring. Referring now to Figure 9 of the drawings, this shows section corresponαing to Figure 8 but in which the edges 22, 23 of .the clamping member parts 14, 15 are upturneα in simpler section than that of Figure 8. However, deformatio of strap 17 into too tight raαii at these edges is stil avoiαeα. The free enαs of parts 14, 15 may also be upturne to proviαe aααitional rigiαity ana provide a local radius to prevent damage to the spring. Referring back now to Figure 5 of the drawings, thi shows a further feature accorαing to a moαification of th invention. The part 14 of the clamping member is provided with a formation 24 extenαing towarαs the part 15, which formation engages a corresponαingly shaped recess in th spring itself. Such a recess would be formed durin manufacture of the spring, by subjecting resin impregnate fibres to heat and pressure in a moulα to cure the resin and form the spring to its final shape. The engagement o formation 24 in such recess provide for positive location o the clamping member relative to the spring, and is particularly effective as helping to resist forces actin longitudinally of the spring which try to pull the attachmen member 12 from recess 11. The configuration of formation 2 and the corresponding recess in the spring would of course b selected so as not to weaken the spring aαjacent its termina portion. As shown in Figures 5 ana 6, the strap 17 may be a simpl component of uniform width, or it may, as shown in Figures 1 ana 2, be of aifferent widths in its parts overlying th parts 14, 15 of the clamping member. The latter embodimen is advantageous in that it provides a firmer hold of th clamping member adjacent the region where it diverges fro the terminal portion of the spring to contact the bush 12. In the embodiments shown in Figure 5 et seq., element 2 may be extenαe as shown at 25 to contact the clamping member 13 where it αiverges from the terminal portion of the spring. This reinforces the clamping member so that it αoes no αistort under forces acting longitudinally of the sprin tenαing to pull member 12 from recess 11.

Claims: CLAIMS 1. A composite leaf spring including, at an end thereof, a attachment member (12) lying in a recess (11) extendin transversely of a terminal portion (10) of the spring an held therein by a clamping member (13) extending around sai attachment member (12) and terminal portion (10) and having part (14,15) extending along spaced surfaces of a spring part (16 adjacent said terminal portion, (10) characterised in tha said clamping member (13) is held to the spring (16) by a shee metal element (17) extending transversely around said part (14,15) of the clamping member (13) and deformed int engagement with recess means (19) in or associated therewith. 2. A spring according to Claim 1 further characterised i that'said recess means (19) is formed in at least one of sai parts (14,15) of the clamping member (13). 3. A spring according to Claim 1 or Claim 2 furthe characterised in that said recess means (19) comprises a aperture. 4. A spring according to Claim 1 further characterised i that said recess means is provided in a further elemen (20,21) interposed between said sheet metal element (17) an the or each said part (14,15) of the clamping member(13). 5. A spring according to Claim 1 or Claim 2 further characterised in that said recess means is defined by a upturned edge portion (22,23) or portions on at least one of said parts (14,15) of the clamping member (13). 6. A spring according to Claim 5 further characterised i that said edge portion (22,23) or portions is of configuration such as to prevent said sheet metal element (17) from being bent in too tight a radius. 7. A spring according to any one of the preceding claim further characterised in that said clamping member (13 incluαes a protruαing formation (24) engaging in correspondingly shaped recess in the spring (16) adjacen saiα terminal portion thereof.

Inventors: HEMMINGS GRAHAM, TUCKER-PEAKE ADRIAN, HEMMINGS, GRAHAM, TUCKER-PEAKE, ADRIAN
Applicants: GKN TECHNOLOGY LTD, GKN TECHNOLOGY LIMITED
Application year: 1984
Main classification: F16F1
IPC codes: B60G11, F16F1