MULTISTABLE ELEMENT

Abstract

The present invention relates to a spring element having two bistable flat springs and two flat connecting elements which are arranged at the longitudinal ends of the bistable flat springs, which are aligned parallel to one another, and connect them to one another.

Description

The invention belongs to the field of flat springs with different operating conditions, which are used as components of bracelets, so far having the following shortcomings: Design limitations that make it difficult or in some cases impossible to integrate the spring into a product because there are no options for mounting external elements or known solutions lead to changes in the spring properties and reduction of its service life.

The multistable element according to the invention has two bistable flat springs held together by two flat rigid plates (2) located at the opposite ends and parallel to the roll-up axis (A) of the springs (FIG. 2a). This leaves a rectangular gap (3) between the flat springs, as can be seen on FIG. 1.

FIG. 1 shows: bistable element in unbent state: 1—bistable springs; 2—rigid plate; 3—gap between bistable springs; 4—welds; 5—polymer layer; 6—optional kink lines on bistable springs; 7—kink lines at the ends of the spring.

Bistable springs have the shape of an elongated (metal) plate, which has a (uniformly) curved/arched shape transverse to its longitudinal direction B (FIG. 3). Due to this shape, bistable springs are characterized by form stability in two different states. As known, for example, from toy slap bracelets, a bistable spring is form stable when it is linearly oriented, as shown in FIG. 1. When a first bending resistance is overcome, the spring rolls/bends into a form stable second state with a defined radius (see FIG. 2a).

In the embodiment according to the invention, the rigid plates are attached to the bistable springs by laser welding with a curved shape seam (4) that overlaps the plate to a depth equal to the width of a spring. The edges of all parts in areas of connection preferably have rounded chamfers. The part of the bistable spring that lies on the plate is flattened. Preferably the kink line (7) located at end portions of the bistable spring is formed. An end portion can be described as a part of the bistable spring close to the rigid plates, in particular in a transition zone to a part of the bistable spring that is connected to the rigid plate.

Basically, a kink is preferably a narrow, straight section of a spring element where the original curve in a cross-sectional view becomes a straight line. Looking at the spring from the side, it may look like a wave. On the whole surface of the springs except the ends, an elastic polymer layer (5) may be applied, which not only serves for damping the bending/unbending process and prolonging the life of the spring, but also decreases the noise when the element is operated. The bistable springs can have additional kink lines (6). The kink lines are provided to separate individual sections of the bistable spring. Consequently, activation of an individual section only leads to a change of shape for that activated part whereby separated sections of the bistable spring remain in their original (elongated) alignment.

According to a preferred embodiment kink lines are provided on each end of at least one bistable spring next to the rigid plates. Thereby the two bistable springs are decoupled and a transition of a bending force is not transmitted from one spring to the other. Consequently, both springs need to be activated (e.g. pressed against) to allow for the bistable element to actually change into a rolled form.

The combination of at least two bistable springs with kink lines at the ends and their connection by rigid plates has the following technical advantages:

1. Slap bracelets (hence a single bistable spring) tend to leave the linear stable state and change to the bent stable state already in case of slight vibrations or touches as well as in case of punctual straightening of the bent/arched shape transversely to its longitudinal direction.

Insofar as only one of the at least two interconnected bistable springs is influenced in this described way, the influenced spring nevertheless retains its flat orientation/state, since the second (non-influenced) spring offers sufficient resistance to the urge of the first spring to change its state. This is particularly supported by the above described decoupling due to kink lines located at the ends of bistable springs in front of the rigid plates which isolate the influence at the central part of the first spring from its ends. In this case, the interconnected springs can be identical.

The second spring thus stabilizes the first spring in its linear state. Only when both/all springs are manipulated, the multistable spring, hence the bistable element, changes its shape/stable state into a bent stable state (FIG. 2a).

This increases the overall shape stability and reduces the sensitivity to trigger the shape change by point pressure.

2. In the unbent/linear state, the element has one of the stable states and thus has an almost flat shape, as can be seen on FIG. 1. In this case, the height (h) of the arch in cross-section, perpendicular to the main axis B of the whole element, is less than the height (H) of a single bistable spring with similar dimensions (FIG. 3) in width as the two individual bistable springs combined. This may be important for bracelets with small thickness and for wide bracelets.

In the collapsed state, the element is in the second stable state and has a curved shape with a defined radius, as shown in FIG. 2a. During the transition from one stable state to the other, the element may be in a metastable transition position, as shown on FIG. 2b. Multi-stable element (FIG. 2a) in collapsed form (FIG. 2b—metastable transition position).

3. The element passes from one state to the other only by external influence to overcome its stable form. The force required to bring the multi-stable element from one state to the other and the radius of the shape that the element takes in the collapsed state depends on the parameters of the bistable springs, such as the type of material, geometric shape of the spring and the gap between them, the places and number of kink lines, parameters of the laminating layer, processing parameters.

These are determined in the design and manufacturing phase, in connection with the technical requirements of the whole bracelet construction.

4. The bistable element can be repeatedly transferred from one state to another by external action, e.g. by fixing the flat plate on one side of the element and applying force to the plate on the other side of the element, perpendicular to the bending axis A of the bistable springs and to the main axis B of the whole element.

5. The element takes a curved shape with a defined radius each time it goes into the collapsed state, and a straight shape along its longitudinal axis B in the unbent state, which it retains. When transitioning from one state to the other, the element can take metastable transitional states due to additional predetermined kink lines on the springs.

6. In addition, the multistable element can be equipped, among other things, with an elastic sheathing, which can be fixed through the gap between the springs, and also with hard external elements, which are fixed to the flat plates. In this case, the functionality of the element, as well as the service life is maintained to 100000 times of bending or more.

DESCRIPTION OF THE INVENTION

The multi-stable element (bistable element) consists of at least two bistable (flat) springs and two (flat) rigid plates attached to them parallel to the bending axis of the bistable springs, one plate being attached to the two springs on one side and the other plate on the other side so that there is preferably a gap between the springs.

The connection points between the elements are preferably laser welded, preferably with a curved seam so that the end of the spring is flattened and overlaps the plate to a depth equal to the width of a spring. This creates a particularly stable connection between the springs and the plates, which nevertheless does not adversely affect the bending property. The open (working) parts of the springs have preferably an elastic polymer coating and/or preferably additional kink lines. The element can be repeatedly transferred from one stable to the other stable state by external action, by fixing the flat plate on one side of the element and applying force to the plate on the other side of the element, perpendicular to the bending axis A of the bistable springs and to the main axis B of the whole element. In this case, the element retains a straight shape when unfolded and a curved, ring-like shape when bent.

It stands out in that

an influence at the middle part of one bistable spring is isolated from an influence at the ends of the bistable spring on the opposite side of the kink lines and vice versa—the impact on the ends of the spring does not affect its middle part. Accordingly, it is possible to rigidly fix the bistable spring by their ends onto the plates and even at least partially flatten them. The impact on a middle part of one spring will not be transmitted to another bistable spring connected via the rigid plates.

Various structural elements can be attached to the flat plates while maintaining the service life of the springs. The height of the arch in cross section, perpendicular to the main axis B (FIG. 3a/3b) of the whole element, is preferably less than the height of the arch of a bistable spring with similar dimensions as described above. The noise level of the element during transition from one state to the other is lower than that of a single bistable spring with similar dimensions. During the transition from one state to another, the element can take a (dynamic) metastable transition states.

• • 1. There are wide possibilities of fixing various external parts to the element, thanks to the flat plates and the preferred gap between the springs, which also allow the multistable element to be incorporated into the housings of other products, in particular, bracelets.
  • 2. The service life of the bistable springs is maintained by the special design of the element, in addition to the extended fastening options of external parts.
  • 3. The possibilities of incorporating the bistable element into flat constructions is increased, thanks to the height of the arch in the cross-section, perpendicular to the main axis B of the whole element, which is less than the height of the arch of a bistable spring with similar dimensions.
  • 4. Quiet noise when folding thanks to the laminated layer on the open part of the springs and the smaller height (h) compared to a single bistable spring with a width of two parallel springs.
  • 5. The bistable element only changes its state if both bistable springs are manipulated.

Links

• • RU2547815C2—Bistable Electromagnetic Drive—Google Patents
  • US20130321759A1—Slap Bracelet Eyeglasses—Google Patents
  • US20120324945A1—Dual function bracelet—Google Patents
  • Bistability—Wikipedia (wikipedia.org)
  • https://ru.wikipedia.org/wiki/%D0%91%D0%B8%D1%81%D1%82%D0%B0%D0%B1%D0%B8%D0%BB%D1%8C%D0%BD%D0%BE%D1%81%D1%82%D1%8C
  • Multistability—Wikipedia
  • Metastable state—Wikipedia (wikipedia.org)

Claims

1. Spring element with at least two bistable springs andtwo flat connecting elements, which are arranged at the longitudinal ends of the bistable flat springs aligned parallel to each other and connecting the two bistable springs to each othercharacterized in thatat least one, preferably two, kink line is arranged on each bistable spring subdividing each of the bistable springs into at least two areas,at least one of the areas is separately, thus individually, releasable from a linear state into a curved state.

2. Spring element according to claim 1characterized in thatthat bistable springs are flattened at the ends.

3. Spring element according to claim 1characterized in thatthat a gap is provided between the parallel aligned bistable flat springs.

4. Spring element according to claim 1characterized in that pthat the bending axes of the flat springs extend transversely to the longitudinal direction of the flat springs.

5. Spring element according to claim 1characterized in thatthat the flat springs and the connecting elements are point-connected.

6. Spring element according to claim 1characterized in thatthat the spot connection is laser welded.

7. Spring element according to claim 1characterized in thatthat the flat springs and the connecting elements are connected by a curved laser weld.

8. Spring element according to claim 1characterized in thatthat the connecting elements are designed as flat rigid plates.

9. Spring element according to claim 1characterized in thatthat the connecting elements and the flat springs overlap to a depth equal to the width of a flat spring.

10. Spring element according to claim 1characterized in thatthe kink lines are arranged on the individual end portions of the bistable springs next to the connection part of the individual bistable spring with each flat connecting element separating the part of the bistable spring that is attached to the flat connecting element from the rest of the bistable spring.