From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specification for a leaf spring assembly with interlocking plates.
| Identifier | ExFiles\Box 154\1\ scan0029 | |
| Date | 7th June 1921 guessed | |
| Similar reference characters refer to similar parts in the different figures. Referring particularly to Figs. 1 and 2, 1, 1 indicate the plates, the same being of maximum width midway of their lengths, and tapering toward their ends, as shown. The spring is shown in Fig. 2 under load; obviously, in its no-load position the plates assume their natural curvature which is imparted to them in the forming operation. The plates 1, 1 being of the same length, and all having the same curvature, they can be formed one upon the other, simply by thinning them slightly toward their ends, as shown; when thus thinned, the under surface of one plate has the same curvature as the top surface of the plate directly beneath it. In the form shown in Figs. 3, 4 and 5, each plate has a spherical enlargement 2 at each end, which may be forged, welded or otherwise formed thereon. These enlargements are adapted to seat in correspondingly shaped recesses of the shackles 3, 3, and because of the bearing space required by each enlargement, it becomes desirable to dispose them in staggered relation within the shackle in order to bring the leaves or plates 1, 1 sufficiently close together. To this end each alternate leaf is disposed with its longitudinal axis at an angle with the axes of the other leaves, as clearly shown in Fig. 1, all of these axes intersecting at the center of the spring. To accommodate the spherical enlargements 2, each shackle 3 is preferably made in sections. A central section 4 provides hemispherical recesses on each side in staggered relation, and preferably has lubricant passageways 5, 5, communicating with said recesses. Outer sections 6, 6 are provided with hemispherical recesses which match up with the recesses of the section 4 on each side to provide bearings for the ends 2 of the spring plates, as shown, the parts being assembled in place and afterward the sections 4, 4 and 6, 6 being fastened together by bolts 7, 7 at their ends, to form the shackle. The inner face of the shackle thus formed is suitably recessed as at 8, 8 to permit of free and unobstructed movement of the spring leaves on the bearings provided by their ends. With the ends of the leaves 1, 1 thus secured for the necessary movement in the shackle or shackles, it will be seen that a semi-elliptic spring is thereby formed, which may have, at its center, the usual seat 9 through which all of the leaves pass, the leaves at this point being separated, if desired, by fillers 9'. The length of seating surface is very much reduced, in comparison to springs of ordinary construction, where the long seats render a considerable length of the spring ineffective. A spring of the form shown in Figs. 1 and 2 does not need a long seat, since the central section thereof, where the seating is disposed, is not weakened by the presence of any center bolt such as is used in the ordinary type of leaf spring. According to the invention as herein disclosed, the spring is made up of one or more leaves or plates, the cross section of each leaf or plate varying along the whole length thereof in such a manner that the strength at any given section is approximately in proportion to the load stress on the spring at such section. In this manner the strength of the whole spring is distributed evenly throughout its length with respect to the load which it is to sustain. Obviously, a spring having the foregoing characteristics and made with leaves or plates 1, 1, all of the same length but of varying cross section, may be embodied not only in the semi-elliptic form herein shown by way of illustration, but also in all the other forms of leaf springs now in common use, such as quarter-elliptic, three-quarters elliptic, full elliptic, cantaliver and plat form. The disposition of the leaves or plates in such form and the arrangement of parts, such as shackles, seats and the like, to accomplish these results, is merely a matter of adapting the known expedients in the spring making art to the novel form and assemblage of leaves herein described. The invention is susceptible, obviously, to various changes in the arrangement of leaves and in the manner of attaching the same to the shackles, it being clear that many modifications with respect to these features will suggest themselves to those skilled in the art. For example, as shown in Fig. 7, the staggered arrangement of the ends of the leaves may be dispensed with, and, if desired, the shackle 10 may be recessed at 11 to receive a row of cylindrical lugs 12, either attached to or formed integral with the ends of the leaves. If desired, the recesses 11 may be in the form of elongated slots, to receive the lugs 12 with freedom for the latter's movement therein, thus compensating for any inequality in the lengths of the leaves. After assembling, the spaces around the lugs within the recesses may be filled up with a bearing metal 11'. Springs made in accordance with my invention have an important advantage in manufacture, in that all the leaves or plates are duplicates, both in size and in curvature. Furthermore, the necessity for sawing the leaves and for the usually practised expedients of beading, lipping, clipping and ribbing, is wholly eliminated, since each plate is independently attached to its shackle, and need not be attached to any other plate. In this connection, it will be clear that the nibs, dowels, corrugations and center bolts ordinarily employed on leaf springs are wholly dispensed with by my | ||