Spring devices – Bendable along flat surface – Bow spring or superposed spring elements
Patent
1989-04-24
1991-05-07
Reger, Duane A.
Spring devices
Bendable along flat surface
Bow spring or superposed spring elements
267 32, 267148, F16F 144
Patent
active
050130137
DESCRIPTION:
BRIEF SUMMARY
This invention relates to springs of the type which comprises a strip of fibre-reinforced plastics material in the form of a zig-zag, having a plurality of limbs connected by reflex portions with the longitudinal centre line of the strip lying substantially in a single plane. Throughout its length, the strip is flat when viewed in cross-section. Such springs are disclosed in international patent application publication no. W085/00207, wherein they are referred to as "sulcated springs", which term will also be used herein for such springs. More particular, the invention relates to arrangements by which such springs can be mounted to other components, for use, for example, as part of a vehicle suspension arrangement.
Sulcated springs have been proposed for use in motor vehicle suspension systems, where the configuration and property of such springs can be advantageous. As compared with conventional coil springs of steel, the use of sulcated springs can lead to a reduction in weight and certain installation advantages resulting from the reduced space occupied by the spring. A sulcated spring is used as a compression spring, loaded between mounting components secured to opposite ends of the spring, and when the spring is loaded the limbs thereof are moved closer together whilst the spring bends at its reflex portions.
The life of a sulcated spring depends inter alia on the angles through which the reflex portions thereof are made to bend when the spring is compressed in use. Simply to clamp an end limb of the spring at an orientation chosen arbitrarily to interfit with the component to which the end limb is clamped is not likely to be satisfactory, since when the spring is compressed one reflex portion of the spring will bend through a greater angle than the other reflex portions of the spring. This can be detrimental to the life of the spring. For example, sulcated spring mountings wherein end limbs of the spring are held at arbitrarily chosen angles are disclosed in international patent application publication no. W087/00252, and while such spring mountings are likely to perform satisfactorily they will not provide optimum operating conditions for the spring because they do not take into consideration the manner in which the springs are deflected as they are compressed. In some of the disclosed spring mountings, end limbs of the spring are bent out of the flat cross-sectional shape of the rest of the strip constituting the spring, to engage in frusto-conical sockets, which is likely further to have a disadvantageous effect on the mode of deflection of the spring in use.
It is the object of the present invention to provide a spring assembly wherein the above described potential disadvantage is overcome or reduced.
According to the invention, I provide a spring assembly comprising a sulcated spring and a member holding an end portion of the spring, wherein the member holds the end portion of the spring by means arranged such that a short length of the reflex portion of the spring at such end portion thereof undergoes substantially no angular movement as the spring is compressed.
As is described in greater detail hereafter with reference to the drawings, holding an end portion of the spring in the manner of the invention has an effect on the behaviour of the spring which is equivalent to pin jointing an end zig-zag limb of the spring at its midpoint. Pin jointing spring end limbs in this way and applying forces to the spring at such pin joints has hitherto been considered the only means by which a sulcated spring can be made to compress uniformly along its length. However, according to the invention, uniform bending of all the reflex portions of the spring when the spring is compressed is obtained, and alternate limbs of the spring remain parallel to one another. The invention thus has the beneficial effect of providing a potential improvement in the life of the spring.
The end portion of the spring which is held preferably comprises an end limb thereof extending generally lengthwise of the spring as a whole, a
REFERENCES:
patent: 315176 (1885-04-01), Smith
patent: 1892198 (1932-12-01), Yevseyeff
patent: 2363837 (1944-11-01), Daugherty
patent: 2594665 (1952-04-01), Lockwood
patent: 3390873 (1968-07-01), Wallerstein, Jr.
patent: 4436201 (1984-03-01), Inaba
GKN Technology Limited
Reger Duane A.
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