CN217355206U - Novel double-shaft flexible hinge for medical prosthesis - Google Patents
Novel double-shaft flexible hinge for medical prosthesis Download PDFInfo
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- CN217355206U CN217355206U CN202122859193.4U CN202122859193U CN217355206U CN 217355206 U CN217355206 U CN 217355206U CN 202122859193 U CN202122859193 U CN 202122859193U CN 217355206 U CN217355206 U CN 217355206U
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Abstract
The embodiment of the utility model discloses a novel flexible hinge of biax for medical prosthesis, including first rigid block, the second rigid block that is located both ends and be in flexible breach district between the two, flexible breach district is oval with the transverse section of perpendicular to along holistic axis. Adopt the utility model discloses, solved current rectangular cross section biax flexible hinge transverse section apex department stress concentration and lead to the cross-section buckling deformation problem more easily effectively, avoided restriction turned angle, improved crooked flexibility stroke, improved fatigue life.
Description
Technical Field
The utility model relates to a flexible hinge technical field especially relates to a novel biax flexible hinge for medical prosthesis.
Background
Compliant mechanism (flexible mechanism) refers to a special mechanism that transfers or converts force, motion or energy by utilizing elastic deformation of its constituent materials. Compared with the traditional rigid mechanism, the flexible mechanism has the advantages of no gap, no assembly, no lubrication and the like, is more in line with the motion connection characteristic of a biological structure, and has wide application prospect in the fields of biomedical engineering and the like. Fig. 1 shows a rigid four-bar linkage in contrast to a flexible four-bar linkage.
A flexible hinge (flexible kinematic pair) is one of the core members of the compliant mechanism. A flexible hinge refers to a kinematic pair structure that utilizes elastic deformation of a material to produce relative motion between adjacent rigid rods under the action of an external force or moment. The performance of the flexible mechanism is largely determined by the characteristics of the flexible hinge.
The flexible hinge can be formed by constructing a relatively thin area with a specific shape on the rigid component, and the thin area (flexible hinge) is more prone to bending deformation under external action, so that the rigid structures at two ends of the flexible hinge move relatively to realize the transmission effect. The notch-type flexible hinge is the most common structure, and two types of structures were reported earlier by Paros in the book to design flexible hinges in 1965: a stretch notch type uniaxial flexible hinge and a swing notch type multiaxial flexible hinge as shown in fig. 2(a) and (b).
The stretching notch type flexible hinge only has one main rotating shaft which is easy to bend under the action of space bending moment, so the stretching notch type flexible hinge is called a single-shaft flexible hinge. Similarly, the main rotation axis of the swing notch type flexible hinge in space is arbitrary, and is called a multi-axis flexible hinge.
To achieve spatial coupling of two rotational directions (two main axes), paras et al also propose an orthogonal tandem stretch notch type flexible hinge shown in fig. 2(c) having two main axes of rotation that intersect spatially, which can be referred to as a biaxial flexible hinge, which can also be referred to as a flexure mechanism.
Lobontiu et al, 2003, in Two-axis flexible joints with orthogonal cross-sectional and symmetric joints, have proposed an orthogonal cross-sectional, in-line, elongated notch-type flexible hinge as shown in FIG. 2(d), which allows Two main axes of rotation to be spatially intersected, which allows for a more compact design and avoids parasitic motion introduced by spatial cross-rotation relative to the flexible hinge structure of FIG. 2 (c).
Flexible hinges have a variety of structural forms and methods of construction, and a variety of structures have been developed in recent years, such as the large number of flexible hinge units provided in the theory and examples of compliant mechanism design (Howell et al, chen gui ji yi et al) books. But the biaxial flexible hinge still only has two types of orthogonal tandem type stretching notch types and orthogonal in-place type stretching notch types with rectangular cross sections.
The space requirement is increased by the existing orthogonal tandem type double-shaft flexible hinge, and the rotating shafts are mutually perpendicular and crossed in space and are not intersected, so that parasitic motion is easily introduced.
Although two main rotating shafts of the existing orthogonal homonymous double-shaft flexible hinge with the rectangular cross section can be mutually and vertically intersected, the cross section of the existing orthogonal homonymous double-shaft flexible hinge is rectangular, as shown in fig. 3, the stress concentration phenomenon exists at the vertex of the rectangle, the rotating angle is limited, the fatigue life is shortened, and the expansion risk of microcracks is increased.
The rotary notch type multi-axis flexible hinge has the same anisotropic rotational rigidity and is not suitable for occasions with anisotropic rigidity requirements.
Disclosure of Invention
The embodiment of the utility model provides a technical problem that will solve provides a novel biax flexible hinge for medical prosthesis. The flexible hinge can solve the problem of stress concentration at the vertex of the cross section of the flexible hinge, improve the bending flexibility stroke and prolong the fatigue life, and can be used as the main body structure of medical prostheses such as artificial intervertebral discs and the like.
In order to solve the technical problem, the embodiment of the utility model provides a novel flexible hinge of biax for medical prosthesis, including first rigid block, the second rigid block that is located both ends and being in flexible breach district between the two, flexible breach district is oval with the perpendicular to along the transversal cross-section of whole axis.
Wherein, the central axis can be a straight line, a curve or a combination of the two.
The flexible notch area is symmetrical about the central axis along the outer contour line on the longitudinal section of the whole central axis.
The flexible notch area is different in distances from the vertex of the long shaft and the vertex of the short shaft of the cross section ellipse to the central axis.
The outline of the flexible notch area on the longitudinal section along the longitudinal section where the trajectory lines of the vertexes of the major axis and the minor axis of the transverse section ellipse are located is one of a straight line, a conical curve, a secant line, a sinusoidal curve, an exponential sinusoidal curve, a cycloid and a parameter polynomial curve or a combination of the straight line, the conical curve, the secant line, the sinusoidal curve and the exponential sinusoidal curve.
Wherein, the radial dimension of flexible breach district presents both ends to the center taper change.
Implement the embodiment of the utility model provides a, following beneficial effect has: the utility model discloses solved current present rectangular cross section biax flexible hinge transverse section apex department stress concentration problem effectively, avoided restriction turned angle, improved crooked flexibility stroke, improved fatigue life.
Drawings
FIG. 1 is a schematic diagram of a comparison structure between a prior art rigid four-bar linkage and a prior art flexible four-bar linkage;
FIG. 2 is a schematic view of a prior art notch-type flexible hinge type;
the flexible hinge comprises a stretching notch type single-shaft flexible hinge, (b) a rotating notch type multi-shaft flexible hinge, (c) an orthogonal tandem type stretching notch type double-shaft flexible hinge, and (d) an orthogonal homonymy type stretching notch type double-shaft flexible hinge with a rectangular cross section;
FIG. 3 is a schematic view of a rectangular cross-section orthogonal in-line stretch-notch type biaxial flexible hinge structure;
FIG. 4 is a three-view diagram of the novel dual-axis flexible hinge structure with an oval cross-section according to the present invention;
FIG. 5 is a result of a finite element analysis of the present invention;
FIG. 6 is an exemplary illustration of a first longitudinal cross-sectional notch profile curve and a second longitudinal cross-sectional notch profile curve along a straight line or a curved line having the same longitudinal length;
FIG. 7 is a combination of two longitudinal cross-sectional profile lines for an "ellipse" - "true circle";
FIG. 8 is a combination of two longitudinal cross-sectional profile embodiments for "ellipse" - "parabola";
FIG. 9 is a combination of two longitudinal cross-sectional profile lines for a "cycloid" - "ellipse";
figure 10 is an example used to compare the performance of two flexible hinges.
Fig. 11 is a structural comparison example of the linear axis and the curved axis, and the cross section and the variable cross section of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 4, the novel dual-axis flexible hinge for a medical prosthesis according to the embodiment of the present invention includes a flexible notch region 1, and a first relatively rigid block 2 and a second relatively rigid block 3 connected to both ends of the flexible notch region as a whole, wherein 4 is a geometric central axis running through structures 1, 2 and 3.
For convenience of explanation, the cross section is defined as a cross section by using a cross section perpendicular to the central axis shown in fig. 4, and the cross section and the longitudinal section are defined as longitudinal sections by using a cross section including the central axis.
Wherein, the transverse section 11 is a section A-A obtained by the area of the flexible notch area 1 and being vertical to the central axis 4, and the longitudinal section 12 is a section obtained by horizontally cutting a section along the central axis 4 of the flexible notch area 1 as a section B-B.
In this embodiment, the central axis may be a straight line, a curved line, or a combination of both, and in this embodiment, the central axis with a constant straight line is taken as an example for description.
The utility model discloses in, flexible breach district 1 is oval with the perpendicular to along being on the transversal cross-section of whole axis.
As shown in fig. 4, the outer contour line of the flexible notch region in the longitudinal section of the central axis of the whole is symmetrical about the central axis, specifically, the outer contour line of the flexible notch region 1 in the longitudinal section 12 is a pair of longitudinal section notch contour curves one 13 symmetrical about the central axis, and similarly, the longitudinal section notch contour curve two 14 in the front view, that is, the major axis vertex of the ellipse presented on the cross section 11 is on the longitudinal section notch contour curve two 14, and the minor axis vertex is on the longitudinal section notch contour curve one 13.
The cross-section of the flexible relief area is symmetrical about the center.
On the basis, when the transverse section A-A moves along the central axis 4, the length of the long axis and the short axis of the transverse section 11 is respectively equal to the minimum distance from the intersection point of the longitudinal section notch profile curve II 14 and the longitudinal section notch profile curve I13 with the transverse section 11 to the central axis 4, and the flexible notch area is gradually changed from two ends to the center.
The distances between the vertexes of the major axis and the minor axis of the ellipse and the central axis are different.
The first profile curve 13 and the second profile curve 14 can be straight lines or curves or a combination thereof with the same longitudinal length, and the distances from the two curves to the central axis 4 are different; wherein, the contour curve (trajectory line) is one of straight line, conic curve, secant, sine curve, exponential sine curve, cycloid, parameter polynomial curve (such as segmented spline function interpolation curve, segmented Hermite polynomial interpolation curve) or their combination.
The flexible notch area 1 is a main deformation area when the flexible hinge works, two ends of the flexible notch area are respectively connected with the relative rigid blocks, the principle of the flexible notch area is equivalent to that of a notch constructed on a rigid structure, a relatively weak structure is realized, the flexible notch area is easy to bend and deform under the action of external force, and movement, force or energy transfer is realized. In particular, as can be seen from the front view and the top view (longitudinal section) of the three views in fig. 4, the notch is formed in a semicircular shape having an equal radius, but the distance between the profile curve of the notch in the longitudinal section and the central axis is not equal. Further, as can be seen from the left view (cross section) of the three views, the cross section in the flexible notch area is an ellipse, and the vertexes of the major axis and the minor axis of the flexible notch area are respectively on the notch profile curve II of the longitudinal section and the notch profile curve I of the longitudinal section.
FIG. 5 shows the finite element analysis result of this embodiment, which is bounded by the condition that one end is fixed and the other end is applied with a pure bending moment. In fig. 5, the two-directional rotational deformation is obtained by applying pure bending moments about the Z axis and about the Y axis in units of 5(a) and 5(b), respectively, and the two-directional flexibility is not equal from the structural deformation and the stress state.
As shown in fig. 6, the present invention further provides an embodiment of the longitudinal section notch profile curve one 13 and the longitudinal section notch profile curve two 14 which can be straight lines or curved lines with equal longitudinal length, in fig. 6, (a) circle, (b) ellipse, (c) straight line, (d) parabola, (e) hyperbola, (f) cycloid, (g) power function, (h) circle-straight line combination (also called fillet type), and (i) circle-cycloid combination.
Fig. 7 shows an embodiment of a combination of two longitudinal sectional profiles from "ellipse" to "perfect circle", wherein the front view notch curve is an ellipse and the top view notch curve is a perfect circle.
As shown in fig. 8, it relates to two combined embodiments of the longitudinal section contour from "ellipse" to "parabola", wherein the front view notch curve is an ellipse, and the top view notch curve is a parabola.
Fig. 9 shows a combined embodiment of two longitudinal section contour lines of "cycloid" - "ellipse", wherein the front view notch curve is cycloid and the top view notch curve is ellipse.
The utility model discloses with the "flexibility/stress ratio" performance index contrast of current rectangle transection cross-section biax flexible hinge.
Flexibility: the inverse of stiffness, consisting of:F=k·xthe method comprises the following steps:c·F=x. The unit can be applied by fixing one end of the flexible hinge and leaving the other end free (i.e., cantilever beam condition), with the free end·The movement (displacement/rotation angle) of the free end under load (force/bending moment) is the compliance. For example, the compliance from rotation about the y-axis is:C θyMy =θ y /M y as shown in fig. 10.
Flexibility/stress ratio: in the process of calculating the flexibility, when the tail end of the flexible hinge bends under the action of unit load, stress is generated in the notch, and the larger value of the flexibility/stress ratio indicates that the stress level is lower under the condition that the flexible hinge generates the same flexibility (displacement/corner), or the higher flexibility is generated under the condition of the same stress level, and the fatigue life is longer.
The advantages of large stroke and low stress of the embodiment of the present invention are shown by comparing the performances of the two flexible hinges in fig. 10. FIG. 10 is a comparison of an elliptical cross-section (a) with the same circular arc notch profile as a flexible hinge with a rectangular cross-section (b), the notch profiles being respectively passed throughRAndθ m determining the minimum cross-sectional dimension byt a Andt b and (4) determining.
3 arithmetic examples are designed for flexible hinges with the same arc notch outline in an oval cross section diagram 10 (a) and a rectangular cross section 10(b) respectively for finite element analysis, the structural dimensions are shown in table 1, the materials are selected from aluminum alloys, the flexibility/stress ratio of each arithmetic example is calculated respectively and shown in table 2, and the result shows that the flexibility/stress ratio of the flexible hinge with the oval cross section is 4% -18% higher than that of the flexible hinge with the rectangular cross section in each arithmetic example, namely: with the same notch profile, an elliptical cross-section flexible hinge can produce greater compliance at the same stress level, or, when the same compliance is produced, the stress level is lower and the fatigue life is longer.
Table 1: the major structural dimensions of each of the two examples of 3 flexible hinges in FIG. 11
Table 2: comparison of the results of "compliance/stress ratio" for 3 examples of each of the two types of flex hinges in FIG. 10
The utility model discloses an oval cross-sectional area replaces the rectangle cross-sectional area, eliminates the stress concentration problem on rectangle summit, can realize two crossing main rotation axles in space and the rigid flexibility of two anisotropy simultaneously. Through finite element analysis contrast discovery, the utility model discloses a flexible hinge can realize higher "flexibility/stress" than rectangular cross section, realizes promptly that under the condition of the same rotation flexibility (displacement-power ratio, reciprocal of rigidity), the stress that the structural deformation produced in the flexible hinge region domain is littleer.
The above disclosure is only a preferred embodiment of the present invention, and certainly should not be taken as limiting the scope of the invention, which is defined by the claims and their equivalents.
Claims (6)
1. The utility model provides a novel flexible hinge of biax for medical prosthesis which characterized in that, is located the first rigid piece at both ends, second rigid piece and is in flexible breach district between the two, flexible breach district is oval with the transverse section of perpendicular to along holistic axis.
2. The novel biaxially flexible hinge of claim 1, wherein said flexible notch area may be linear, curvilinear or a combination of both along the overall central axis.
3. The novel biaxial flexible hinge for a medical prosthesis according to claim 2, characterized in that the outer contour lines on a longitudinal section along the central axis of the whole of the flexible notch area are symmetrical about the central axis.
4. The novel biaxial flexible hinge for a medical prosthesis according to claim 3, characterized in that the major and minor axis vertices of the cross section of the flexible notch area are at different distances from the central axis.
5. The novel biaxial flexible hinge for a medical prosthesis according to claim 4, characterized in that the contour line of the flexible notch area on a longitudinal section plane along the trajectory line of the major axis and minor axis vertex of the transverse cross-sectional ellipse is one of a straight line, a conical curve, a secant line, a sinusoidal curve, an exponential sinusoidal curve, a cycloid curve, a parametric polynomial curve or a combination thereof with each other.
6. The novel biaxial flexible hinge for a medical prosthesis according to claim 5, characterized in that the radial dimension of the flexible notch area varies from end to center.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202122859193.4U CN217355206U (en) | 2021-11-19 | 2021-11-19 | Novel double-shaft flexible hinge for medical prosthesis |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202122859193.4U CN217355206U (en) | 2021-11-19 | 2021-11-19 | Novel double-shaft flexible hinge for medical prosthesis |
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| CN217355206U true CN217355206U (en) | 2022-09-02 |
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