Spring devices – Elastic extension devices – Compression spring
Patent
1985-01-28
1987-03-31
Butler, Douglas C.
Spring devices
Elastic extension devices
Compression spring
267 61S, 267 73, 267168, 267177, F16F 112, F16F 304
Patent
active
046537368
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a spring system comprising at least two mainly parallel, e.g. concentric, springs, wherein at least one spring, having a variable spring characteristic, is connected at its one end with one of two parts, between which an elastic force is to be introduced, and at least one other spring is connected at its one end with the other part.
It is known that the spring characteristic of a spring, i.e. the travel of the spring as a function of the elastic force, can be changed by altering the number of the effective turns of the spring, e.g. by means of a clamp which fixes a number of the spring's turns in relation to each other. The elastic force corresponding to a given travel of the spring can thereby be varied, e.g. in a mechanism in which a spring acting as a power spring actuates two parts to move a certain distance towards or away from each other at different loads, i.e. by exerting various spring forces, or in a spring suspension system in which various loads are absorbed, the travels of the spring being unchanged.
If, for example, the same spring is in this way to be made to exert different elastic forces within a predetermined interval, e.g. 50-100 kp, with a constant, likewise predetermined, spring travel, a fairly long and bulky spring must be used, which both permits the deformation corresponding to the desired spring travel at the small force, e.g. 50 kp, and by reduction of the number of effective turns limits the deformation to the same value at the large force, e.g. 100 kp. At the elastic force interval of 50-100 kp chosen as example the slope of the spring characteristic must thus be changed by a factor of 2, and the free spring length, i.e. the total length of the spring without load will be somewhat more than twice the desired spring travel. This means that a solution such as this is often not feasible owing to considerations of space.
From the U.S. Pat. No. 973,641 a spring system is known with two concentric springs, between which a tubular member is provided the ends of which are in mesh between the turns on the innermost and outermost spring, respectively. By turning the tubular member one can increase or diminish the elastic force of the two springs at the same time, but unless other manipulations are made, this also increases or diminishes the resulting elastic force of the system in the initial position, which is often disadvantageous.
A purpose of the present invention is to produce a spring system which in connection with a simple and compact structure and without replacement of the spring permits a particularly large variation in the spring characteristic, i.e. a considerable increase or decrease of the elastic force within a predetermined interval at a predetermined spring travel and with unchanged elastic force in the initial position.
This is obtained by a spring system of the kind referred to above according to the invention by the other opposite ends of the springs being in firmly connection with each other and having a constant distance from each other in the direction of the spring.
As a result of the mutual position and interconnection of the springs it is obtained that the resulting spring travel for the spring system equals the sum of the travels of at least two springs, and as at least one of these has a variable characteristic, a very considerable range of variation for the slope of the system's spring characteristic can be obtained depending on the choice of spring. The total obtainable spring travel that can be made to approach or even exceed the length of the spring system in the initial position also depends on the choice of spring. Moreover, a constant elastic force is obtained in the initial position, if the distance between the parts actuated by the spring system is always the same in the initial position.
In principle, in a spring system according to the invention, an arbitrary number of springs can be used, but in many cases it is sufficient to have two springs, which can be two tension springs, two compression springs or one tension and one
REFERENCES:
patent: 483762 (1882-10-01), Crippen
patent: 973641 (1910-10-01), Dysart
patent: 1260921 (1918-03-01), Leissner
patent: 2222146 (1940-11-01), Jonsson
patent: 2643109 (1953-06-01), Wood
patent: 2969972 (1961-01-01), Holmen
patent: 3399879 (1968-09-01), Hojo et al.
Butler Douglas C.
Diefendorf Richard R.
Flemming HVIDT Mobelarkitektfirma A/S
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