Flexure hinge

Abstract

A flexure hinge with two material segments connected to each other via a material tapering to a thin spot which defines a pivot axis between the two material segments. The material segments are provided with recesses such that the strength existing in the thin spot with respect to normal stresses or bending stresses is kept largely constant within a distance from the thin spot.

Claims

1. A flexure hinge comprising: (a) a first material segment and a second material segment monolithically connected together along a thin spot which defines an imaginary pivot axis between the first material segment and the second material segment, at least one of the first material segment and the second material segment having a thickness along a direction X which tapers in a tapering zone along a direction Y perpendicular to the direction X to a minimal thin spot thickness, the imaginary pivot axis extending in a direction Z perpendicular to the direction X and the direction Y; (b) at least one recess positioned in the tapering zone of the at least one of the first material segment and the second material segment; and (c) wherein the at least one recess is formed so that a direction X and direction Z plane passing through the at least one recess intersects the respective material segment to define a cross section that provides a strength that corresponds, within tolerances, to the strength provided by the cross section defined by the intersection of a direction X and direction Z plane passing through the thin spot.

2. The flexure hinge of claim 1 wherein the cross section defined by a given direction X and direction Y plane passing through the at least one recess comprises a number of cross section areas spaced apart along the direction Z and comprising geometric shapes the width of which along the direction Z decrease with increasing distance along the direction Y from the position of the thin spot along the direction Y.

3. The flexure hinge of claim 2 wherein the at least one recess is formed such that along at least a portion of the length of the at least one recess along the direction Y, the cross section areas define a constant total area regardless of the point along the direction Y at which the given direction X and direction Z plane intersects the at least one recess.

4. The flexure hinge of claim 3 wherein the constant total area is equal to the area defined by the intersection of the direction X and direction Z plane through the thin spot.

5. The flexure hinge of claim 2 wherein the cross section areas spaced apart along the direction Z comprise a plurality of identical geometric shapes.

6. The flexure hinge of claim 1 wherein along at least a portion of the length of the at least one recess along the direction Y, a moment of resistance about the imaginary pivot axis remains constant.

7. The flexure hinge of claim 1 wherein the cross section of the thin spot defined by the intersection of the direction X and direction Z plane at the thin spot has the shape of one or more rectangles.

8. The flexure hinge of claim 1 wherein the at least one recess has an outline in a direction Y and direction Z plane in which: (a) two boundary lines extend away from the thin spot along the direction Y from a common vertex which comprises the part of the at least one recess lying closest to the thin spot; and (b) where one or both boundary lines depart from a plane defined by the direction X and direction Y plane lying at the vertex, the departure being symmetric along a curve with increasing distance from the thin spot along the direction Y.

9. The flexure hinge of claim 8 wherein a segment of the curve is formed in dependence on the material thickness of the tapering zone given at the respective position along the direction Y.

10. The flexure hinge of claim 1 including multiple recesses identical in shape and lying side by side along the direction Z.

11. The flexure hinge of claim 1 wherein one or more recesses are provided along the direction Y in each of the first material segment and the second material segment on both sides of the thin spot.

12. The flexure hinge of claim 11 wherein the first material segment and the second material segment each include a respective tapering zone and at least one recess is provided in each tapering zone and wherein each recess is positioned the same distance from the thin spot along the direction Y.

13. The flexure hinge of claim 1 wherein that the thin spot is divided by at least one opening into a plurality of thin spot segments that lie side by side in the direction Z.

14. A measurement apparatus comprising the flexure hinge of claim 1 wherein the flexure hinge is part of a lever, a coupling rod, a rotating hinge, a free flex pivot hinge, or a parallel arm mechanism.

15. A method for producing a flexure hinge according to claim 1 wherein the at least one recess is introduced into the tapering zone at least in part with a laser applied on both sides of a direction Y and direction Z plane lying at the imaginary pivot axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a perspective view of a flexure hinge according to the invention.

(2) FIG. 2 shows a first perspective section of the hinge shown in FIG. 1.

(3) FIG. 3 shows a second perspective section of the hinge shown in FIG. 1 at a section plane further from the thin spot of the hinge as compared to the section of FIG. 2.

(4) FIG. 4 shows a third perspective section of the hinge shown in FIG. 1 at a section plane further from the thin spot of the hinge as compared to the section of FIG. 3.

(5) FIG. 5 shows a schematic top view of a section of a flexure hinge.

(6) FIG. 6 shows a perspective view of a flexure hinge segment.

DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

(7) FIG. 1 shows a flexure hinge according to the invention in a simplified perspective view. The hinge comprises two material segments M.sub.1, M.sub.2, which are monolithically joined to each other via a thin spot D. The thin spot D is formed by two tapering sections V.sub.1, V.sub.2, which extend in a lengthwise direction Y toward each other as part of the material segments M.sub.1, M.sub.2, where the thickness measured perpendicular thereto in the X direction steadily decreases up to a minimal thickness X.sub.D, at which the actual thin spot D exists. It extends along a pivot axis W.sub.D in a width direction Z, which is perpendicular to the X and Y directions. The first material segment M.sub.1 can be pivoted with respect to the second material segment M.sub.2 about the thin spot D, where an idealized pivot axis W.sub.D runs in the Z direction at the lengthwise position Y.sub.D of the thin spot D. An opening H made centrally in the thin spot D divides the thin spot into two segments Da and Db in the Z direction.

(8) A plurality of recesses U.sub.1, U.sub.2 of which not all are provided with reference numbers in the figures for reasons of clarity, penetrate the first and second tapering zones V.sub.1, V.sub.2 on both sides of the thin spot D (in the Y direction). The recesses U.sub.1, U.sub.2 are chosen so that the strength properties of the hinge at the thin spot D approximately coincide with the strength properties of the hinge at a distance from the thin spot that extends to the recesses U.sub.1, U.sub.2. The following figures explain this characteristic provided by recesses U1, U2 in more detail.

(9) FIG. 2 shows a section of the thin spot D with the width B (in the Z direction), in a magnified and sectioned view. A section plane E.sub.D, which passes through the thin spot in the X-Z direction, produces a section Q.sub.D with cross section area A.sub.D. The resulting cross section area A.sub.D has certain strength properties with respect to the normal stresses in the Y direction or with respect to bending moments about the pivot axis W.sub.D. Since the thin spot D is formed along the imaginary section with B without interruptions, this results in a single cross section area A.sub.D, which has a rectangular shape because of the cylinder section shaped surface of the tapering zones V.sub.1, V.sub.2.

(10) FIG. 3 shows a sectional view comparable to FIG. 2, where in this case a section plane E shifted parallel to section plane E.sub.D in the Y direction passes through the region of the tapering zone V.sub.1, which is penetrated by the recesses U.sub.1. Correspondingly, a number of individual rectangular cross section areas lying side by side in the Z direction, which add up to a total area A, result from the section Q of the plane E with the tapering zone V.sub.1. The individual rectangular areas (up to the segments lying at the edge in the Z direction) have a width R.sub.z. According to the invention the recesses U.sub.1 are chosen so that the resulting cross section area A coincides with the cross section area A.sub.D (area equivalent) formed in the thin spot. From this it follows that a tensile or compressive force in the thin spot D applied to the hinge in the Y direction generates the same stress (=F/A) as in the region of the plane E or the cross section Q that is there.

(11) FIG. 4 shows another cross section Q, which results from the intersection of an additional section plane E parallel to the planes E.sub.D and E, with the tapering zone at a Y position that is still farther from the thin spot than the section plane E, but still within the segment L.sub.U. The resulting cross section area A is further composed of individual rectangles, the width R.sub.z of which (possibly with the exception of the section lying at the edge in the Z direction) is, however, smaller than in the case of cross section Q. However, because the material thickness of the tapering zone V.sub.1 increases with increasing Y distance from the thin spot, the thicknesses R.sub.x, R.sub.x of the individual partial cross section correspondingly increase. As a result, it follows from the shape, chosen per the invention, of the recesses U.sub.1 along the segment L.sub.U that the cross section area A also corresponds with the cross section area A or A.sub.D (area equivalent). This effect, thus the area stress or area load that largely remains constant with increasing Y distance from the thin spot D, applies in the embodiment shown along the selected segment L.sub.U because of the suitable shape of the recesses U.sub.1. The segment L.sub.U can extend over the entire Y length of a recess U.sub.1, U.sub.2 or can involve only a part of it.

(12) An imaginary shift of the section plane E along the segment L.sub.U in this embodiment example always produces a total cross section A, A . . . , the size of which corresponds with that of A.sub.D of the thin spot D.

(13) The flexure hinge represented in FIGS. 2 to 4 was created by means of its recesses U.sub.1, U.sub.2 so that the sections Q.sub.D, Q, and Q formed along the segment L.sub.U always produce the same total cross section area, so that tensile or compressive stresses along the segment L.sub.U and in this respect independent of the Y distance to the thin spot D remain largely constant.

(14) The same principle, which is not shown in the figures, also applies if, instead of the normal stresses, the bending stresses, which result from a bending of the material segments M.sub.1, M.sub.2 relative to each other about the Z axis (moment of resistance equivalent), are to be kept constant. Since the moment of resistance of a cross section area to bending is overproportional to the height of the cross section (in this case on the thickness R.sub.x, R.sub.x of the individual partial cross sections), the recesses U.sub.1, U.sub.2 are chosen correspondingly so that the relevant width R.sub.z, R.sub.z of the partial cross sections is overproportionally reduced with increasing Y distance, in order to produce a constant moment of resistance as a result.

(15) FIG. 5 shows a section of the flexure hinge according to the invention from FIGS. 1 to 4 in a top view in the X direction. The thin spot D extends in the width direction Z along an idealized pivot axis W.sub.D at the Y position of the thin spot, Y.sub.D. In the tapering zones V.sub.1, V.sub.2 on both sides of the thin spot D in the Y direction are approximately triangular recesses U.sub.1, U.sub.2, as was already described in FIGS. 2 to 4. The outline of each recess U.sub.1, U.sub.2 comprises in this case two boundary lines G.sub.a, G.sub.b, which, starting from a common vertex S, extend symmetrically on both sides of an imaginary section plane E.sub.S, which runs in the X-Y direction through the vertex S. The recesses U.sub.1, U.sub.2 are each bounded at their ends turned away from the thin spot D by wall segments running in the Z direction.

(16) As FIG. 5 also shows, the recesses U.sub.1, U.sub.2 do not border directly on the idealized pivot axis W.sub.D of the thin spot D, but rather have a small Y distance from it. To avoid hot spots and undefined weaknesses of the thin spot, the recesses U.sub.1, U.sub.2 first begin at a small Y distance from the thin spot D.

(17) FIG. 6 shows a perspective of a flexure hinge according to the invention with the recesses U.sub.1, U.sub.2 in the tapering zones V.sub.1, V.sub.2.

(18) As used herein, whether in the above description or the following claims, the terms comprising, including, carrying, having, containing, involving, and the like are to be understood to be open-ended, that is, to mean including but not limited to.

(19) Any use of ordinal terms such as first, second, third, etc., in the following claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another, or the temporal order in which acts of a method are performed. Rather, unless specifically stated otherwise, such ordinal terms are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term).

(20) In the above descriptions and the following claims, terms such as top, bottom, upper, lower, and the like with reference to a given feature are intended only to identify a given feature and distinguish that feature from other features. Unless specifically stated otherwise, such terms are not intended to convey any spatial or temporal relationship for the feature relative to any other feature.

(21) The term each may be used in the following claims for convenience in describing characteristics or features of multiple elements, and any such use of the term each is in the inclusive sense unless specifically stated otherwise. For example, if a claim defines two or more elements as each having a characteristic or feature, the use of the term each is not intended to exclude from the claim scope a situation having a third one of the elements which does not have the defined characteristic or feature.

(22) The above described preferred embodiments are intended to illustrate the principles of the invention, but not to limit the scope of the invention. Various other embodiments and modifications to these preferred embodiments may be made by those skilled in the art without departing from the scope of the present invention. For example, in some instances, one or more features disclosed in connection with one embodiment can be used alone or in combination with one or more features of one or more other embodiments. More generally, the various features described herein may be used in any working combination.

REFERENCE NUMBER LIST

(23) X Thickness direction

(24) Y Length direction

(25) Z Width direction

(26) M.sub.1, M.sub.2 Material segment

(27) V.sub.1, V.sub.2 Tapering zone

(28) D Thin spot

(29) Da, Db Thin spot segments

(30) H Opening

(31) W.sub.D Pivot axis

(32) U.sub.1, U.sub.2 Recesses

(33) Q.sub.D Cross section through thin spot D

(34) Q.sub.v, Q.sub.v Cross section through tapering zone

(35) E.sub.D Section plane through thin spot

(36) E, E Section planes through tapering zone

(37) E.sub.S Section plane through tapering zone

(38) B Section width

(39) R.sub.X Thickness of a partial cross section area

(40) R.sub.Z Width of a partial cross section area

(41) A.sub.D Cross section area through the thin spot

(42) A, A Cross section area in the sections Q, Q

(43) L.sub.U Segment section in the Y direction.