WO2001069096A2 - Stable bi-axial pivot flexure coupling - Google Patents
Stable bi-axial pivot flexure coupling Download PDFInfo
- Publication number
- WO2001069096A2 WO2001069096A2 PCT/US2001/008087 US0108087W WO0169096A2 WO 2001069096 A2 WO2001069096 A2 WO 2001069096A2 US 0108087 W US0108087 W US 0108087W WO 0169096 A2 WO0169096 A2 WO 0169096A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- flexures
- axis
- blade
- flexure
- attached
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Ceased
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C11/00—Pivots; Pivotal connections
- F16C11/04—Pivotal connections
- F16C11/12—Pivotal connections incorporating flexible connections, e.g. leaf springs
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T403/00—Joints and connections
- Y10T403/32—Articulated members
- Y10T403/32606—Pivoted
- Y10T403/32861—T-pivot, e.g., wrist pin, etc.
Definitions
- This invention relates to devices for providing low friction, rotational couplings, in particulaj, a stable bi-axial pivot flexure coupling to provide rotationally compliant ends for kinematic linkages
- a simple spherical ball and socket connection provides a coupling that is rotationally compliant and axially stiff .
- a coupling of this type is used as an end fitting for linkages or rods or struts where axial forces must be rigidly transferred, and rotations are relatively unconstrained.
- the ball and socket end connection is however characterized by large friction losses, making it undesirable for low power, precision coupling .and in particular closed loop feedback controls, which can become unstable when too much stick-slip motion is present. Pivot flexures, like the coupling 4 shown in Fig. 4, are generally more useful in those applications.
- This device operates in a completely linear fashion by means of elastically deflecting flexure blades 4a that produce the desired linkage 4c end rotation with a fixed end or other linkage 4d.
- Rotational compliance about the two axes orthogonal to the link axis (direction 4b in figure 4) is desired thus the term biaxial is often used to describe these flexures.
- Some rotational compliance about the link axis is also achieved with this type of flexure although it is not critical in most applications Even though blade type pivot flexures have been used successfully, they possess certain performance limitations, in particular weak axial load carrying capacities.
- the interleaved blades 4a must be slender which makes them susceptible to buckling under compressive or axial loads, in the direction 4b.
- the blades 4a conceivably can be made thicker, which makes them less flexible and increases rotational stiffness reducing the coupling's effectiveness.
- the goal is minimal rotational stiffness, which requires the thinnest possible blades but maximum axial strength.
- An object of the present invention is to provide a biaxial rotational coupling with minimal rotational friction and losses of the blade type and also capable of bearing higher axial compressive loads.
- a stable pivot flexure coupling uses thin flexures (blades) to connect the rotating end members and the pivot joint is located near the midpoint of each flexure.
- a flexure coupling comprises a first end member normal to a load axis (i.e., 4b in figure 4); a second end member normal to said load axis at a first distance from the second end member; an aperture in said first end member on said axis; an aperture in said second end member on said axis; first and second flexures connecting sadd end members, s.aid first and second flexures being parallel to said load axis and diametrically opposed; third and fourth flexures connecting said end members, said third and fourth flexures being parallel to said load axis and diametrically opposed; a first cross member normal to said load axis and connected near the midpoints of the first and second flexures ; a first rod along said axis and extending through the aperture in said first end member and attached to said first cross member; a second cross member normal to said axis and connected near the midpoints of the third and fourth flexures; a second rod along said .axis and extending through
- four axial connecting rigid spacers diametrically arranged, secure the first and second end members with the flexures located between the end members and the spacers to form a cage for the flexures.
- each flexure is formed with base at each end which is secured to the end members with the rigid spacers.
- a benefit of the invention is that each blade flexure reacts axial loads in both compression and tension. As a result, flexure failure, i.e., failure of a blade, can only occur when the elastic limit of the flexure material is reached. With the benefit of the previous discussion of the invention, one of ordinary skill in the art may be able to modify the invention in whole or in part without departing from the true scope and spirit of th ⁇ invention.
- FIG. 1 is an elevation of a stable flexure blade assembly embodying the present invention.
- Fig. 2 is a section along line 2-2.
- Fig 3. is a schematic of a coupling having axially opposed connecting rods, each connected to a pair of flexure blades according to the present invention.
- Fig. 4 shows a flexure coupling used in the prior art.
- Fig. 5 is a section along line 5-5 in Fig. 3.
- Fig. 6 is an section along 6-6 in Fig. 8
- Fig. 7 is a section 7-7 along in Fig. 8
- Fig. 8 is a side view of the present invention
- Fig. 9 is a section along 9-9 in Fig. 8
- a flexure blade assembly 9 includes a control rod 10 which is moveable around an axis 12 parallel to cross-member 30 to be able to flex or move (rotate slightly) with respect to fixed circular members 14 and 16. (See angle ⁇ in Figure 2) End members 14 and 16 are connected by thin, leaf like or blade type flexures 18, 20, made of a resilient metal, plastic or composite. It should be noted from schematic Fig. 3 that there are four blade flexures, first and second flexures 18. 20. as mentioned and third and fourth flexures 22, 24, a . ll attached at their ends to the end members 14 and 16. Blade flexures 18, 20 are attached to control rod 10 through cross-member 30 and along a plane, as shown in Fig. 1.
- the second pair of blade flexures 22, 24 He a long a plane normal to the plane of blade flexures 18, 20 and are attached to a second control rod 26 through cross-member 32. (See also Figs. 6 through 9.)
- control rod 10 is orthogonal to similar rotations of control rod 26 by the mechanical connection between the blade flexures and the end members, providing biaxial rotational compliance between the two control rods.
- Control rod 10 is attached to a transverse bar or cross member 30 one end of which 30a is attached, e.g., welded, as close as possible to the middle of blade flexure 18, and likewise the other end 30b is attached to the middle of blade flexure 20.
- Control rod 26 is attached to transverse bar 32 which is similarly attached with its ends 32a, 32b as close as possible to the middle of its respective blade flexures 22, 24, while providing some clearance with transverse bar 30.
- the points 30c and 32c where the rods 10 and 26 attach to their respective bars 30 and 32 are the intermediate blade flexure points.
- the coupling in Figs. 1, 2 and 3 reacts axial loads both in compression and tension through the blade flexure points, such as 32c.
- the load path continues through the transverse bars and then through each blade flexure.
- the load path then splits with a portion of the load causing tension in one part of the blade flexure and another portion of the load causing compression in the other part of the blade flexure .
- the magnitude of the load reacted by each blade flexure segment is dependent on a few factors, since the axial load path becomes statically indeterminate. First, the location of the pivot point along the length of the blade determines relative stiffness by the blade and its reaction to axial loads.
- each blade flexure portion Another factor in determining load magnitude in each blade flexure portion is the compression portion of the blade flexure and its buckling stability. If the compression side is not stable to the load the flexure will buckle. The tension side must therefore react all the load. In other words, the reaction through the flexures and rods 10 and 26 puts the blade flexures in tension, minimizing the risk of buckling.
- the length of each blade flexure 18, 20, 22, 24 is .75 inches, and the flexure is made of titanium 6A1-4N.
- the connection point 34 is .3 inches and the blade flexure is .013 X .3 inches in cross-section.
- the buckling load for each blade flexure is 90 lbs. This is without adding the additional stresses encountered when the blade is flexed or slightly rotated as shown in Fig. 2. If a blade of the same dimensions and material make-up is configured as the present invention (intermediate blade flexure points), the allowable load for the flexure is increased to 200 pounds. This stable flexure continues to be structurally sound when reacting this load and experiencing 5 degrees ( ⁇ ) of rotation.
- Figs. 6-9 show an embodiment of the basic flexure structure explained above, in assembly that is easy to fabricate.
- This embodiment uses four posts or separators 35, 36, 37 and 38, arranged diametrically and secured to rigid end members 40 by fasteners 39, forming a cage for the flexures 18, 20, 22, 24.
- the flexures are g . iven the previous numbers but are formed with integral bases, e.g., 22a, that are sandwiched between the rigid spacers 35, 36, 37, 38 and the end members 40.
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Wind Motors (AREA)
- Pivots And Pivotal Connections (AREA)
- Joints Allowing Movement (AREA)
- Mutual Connection Of Rods And Tubes (AREA)
- Chairs Characterized By Structure (AREA)
- Cyclones (AREA)
- Fishing Rods (AREA)
- Pens And Brushes (AREA)
- Non-Reversible Transmitting Devices (AREA)
Abstract
Description
Claims
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AU2001245697A AU2001245697A1 (en) | 2000-03-14 | 2001-03-14 | Stable bi-axial pivot flexure coupling |
| DE60111193T DE60111193T2 (en) | 2000-03-14 | 2001-03-14 | STABLE BI-AXIAL BENDED JOINT COUPLING |
| JP2001567946A JP3881552B2 (en) | 2000-03-14 | 2001-03-14 | Stable biaxial pivot flexure joint |
| AT01918644T ATE296971T1 (en) | 2000-03-14 | 2001-03-14 | STABLE BI-AXIAL FLEXIBLE JOINT COUPLING |
| EP01918644A EP1264111B1 (en) | 2000-03-14 | 2001-03-14 | Stable bi-axial pivot flexure coupling |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US09/525,202 US6318923B1 (en) | 2000-03-14 | 2000-03-14 | Stable bi-axial pivot flexure coupling |
| US09/525,202 | 2000-03-14 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| WO2001069096A2 true WO2001069096A2 (en) | 2001-09-20 |
| WO2001069096A3 WO2001069096A3 (en) | 2001-12-27 |
Family
ID=24092340
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/US2001/008087 Ceased WO2001069096A2 (en) | 2000-03-14 | 2001-03-14 | Stable bi-axial pivot flexure coupling |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US6318923B1 (en) |
| EP (1) | EP1264111B1 (en) |
| JP (1) | JP3881552B2 (en) |
| AT (1) | ATE296971T1 (en) |
| AU (1) | AU2001245697A1 (en) |
| DE (1) | DE60111193T2 (en) |
| WO (1) | WO2001069096A2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20090020303A1 (en) * | 2004-01-29 | 2009-01-22 | Elwyn Gooding | Adaptive, ergonomic, multi-purpose hand-held tool with flexible drive shaft |
| US11821572B2 (en) | 2021-03-18 | 2023-11-21 | Raytheon Company | Laterally compliant mounting structure |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3312458A (en) * | 1963-02-21 | 1967-04-04 | Skf Svenska Kullagerfab Ab | Bearing between two relatively oscillable members for oscillating movement |
| US3272492A (en) * | 1964-03-11 | 1966-09-13 | Northrop Corp | Transversely supported torsion bar |
| US3384424A (en) * | 1966-12-29 | 1968-05-21 | Task Corp | External cross strap elastic pivot |
| FR1561634A (en) * | 1967-04-07 | 1969-03-28 | ||
| US3712081A (en) * | 1971-01-11 | 1973-01-23 | G Philipp | Universal joint for coupling a plurality of shafts |
| US4405184A (en) * | 1981-03-16 | 1983-09-20 | The United States Of America As Represented By The Administrator Of The National Aeonautics And Space Administration | Unidirectional flexural pivot |
| DE3227988C2 (en) * | 1982-07-27 | 1984-05-30 | Dr. Johannes Heidenhain Gmbh, 8225 Traunreut | Shaft coupling |
| DE3241373A1 (en) * | 1982-11-09 | 1984-05-10 | Anschütz & Co GmbH, 2300 Kiel | SPRING JOINT |
| US4802784A (en) * | 1988-03-11 | 1989-02-07 | Santa Barbara Research Center | Bi-flex pivot |
-
2000
- 2000-03-14 US US09/525,202 patent/US6318923B1/en not_active Expired - Lifetime
-
2001
- 2001-03-14 AT AT01918644T patent/ATE296971T1/en not_active IP Right Cessation
- 2001-03-14 AU AU2001245697A patent/AU2001245697A1/en not_active Abandoned
- 2001-03-14 EP EP01918644A patent/EP1264111B1/en not_active Expired - Lifetime
- 2001-03-14 JP JP2001567946A patent/JP3881552B2/en not_active Expired - Fee Related
- 2001-03-14 DE DE60111193T patent/DE60111193T2/en not_active Expired - Lifetime
- 2001-03-14 WO PCT/US2001/008087 patent/WO2001069096A2/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| AU2001245697A1 (en) | 2001-09-24 |
| US6318923B1 (en) | 2001-11-20 |
| JP2003527546A (en) | 2003-09-16 |
| DE60111193D1 (en) | 2005-07-07 |
| JP3881552B2 (en) | 2007-02-14 |
| EP1264111B1 (en) | 2005-06-01 |
| ATE296971T1 (en) | 2005-06-15 |
| WO2001069096A3 (en) | 2001-12-27 |
| DE60111193T2 (en) | 2006-03-16 |
| EP1264111A2 (en) | 2002-12-11 |
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