US 3576136 A
Description (OCR text may contain errors)
United States Patent  Inventor William P. Myers Rock Island, Ill.  Appl. No. 866,235  Filed Oct. 14, 1969  Patented Apr. 27, I971  Assignee The Bendix Corporation  FLEX BAND DEVICES 22 Claims, 13 Drawing Figs.
52 US. Cl 74/892, 74/99, 308/26  Int. Cl ..Fl6h 27/02, Fl6h 21/44, F160 27/00  Field of Search 308/26, 9; 74/99, 89.2
 References Cited UNITED STATES PATENTS 295,587 3/1884 Sadler 74/891 l0/ I956 2/ l964 9/1965 1 H1965 4/1970 4/1970 7/ 1970 Faxin 74/892 Hunter 308/26 Gorgens et al 74/892 Silver etal. 308/26 Gross et al. 308/9 Love 308/9 Licht 308/9 Primary ExaminerWilliam F. ODea Assistant Examiner-Wesley S. Ratliff, .lr. Att0rneyWilliam N. Antonis ABSTRACT: A mechanical movement which comprises a center shaft, a supporting frame, and mechanism for causing said center shaft or said supporting frame to rotate about a fixed axis wherein said mechanism includes a plurality of conjointly movable rockers interposed between the shaft and frame and thin flexible band means operatively connected to said frame, rockers, and shaft for transmitting motion therebetween.
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INVENTOR. WILLIAM F. MYERS ATTORNEY FLEX BAND DEVICES BACKGROUND OF THE INVENTION Normal antifriction bearings such as ball bearings or roller bearings do not eliminate all sliding friction because of the sliding action which occurs between the balls or rollers and the retainers. Additional sliding occurs in such bearings between the rolling elements and the shoulders or races when axial thrust loads are applied. These residual friction forces are dominant factors in the design of sensitive instrument mechanisms with limited energy inputs. Additional accuracy problems arise from the lost motion due to the radial clearances in shaft bearings.
Other bearings, such as jewel bearings, suffer similar friction and clearance problems. In addition, the small shaft diameters, which are used with jewel bearings, are susceptible to shock damage.
Insofar as flexural pivots are concerned, such pivots can eliminate friction and lost motion problems, but they cannot pivot about a fixed axis and are limited to angular movements of approximately 60.
SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a unique arrangement for supporting and rotating a member about a fixed axis with virtually no sliding friction. In order to eliminate such sliding friction, all components are interconnected with a thin flexible band which constrains motion between the parts, maintains alignment, and transfers the necessary operating forces without slippage. In this arrangement rolling friction is very low and the major energy loss is attributed to the internal friction of the flex hand.
More specifically, it is an object of this invention to provide a unique flex band arrangement which can function as:
l. A shaft bearing having virtually no sliding friction;
2. A shaft bearing having no end shake;
3. A shaft bearing which requires no lubrication;
4. A single bearing device capable of withstanding overhanging shaft loads;
5. A shaft drive which translates a nonlinear input into a linear output, or which translates a linear input into a nonlinear output;
6. A single step shaft drive with almost unlimited amplification;
7. A shaft drive which can generate various torsional force and angular displacement curves;
8. A shaft drive having no lost motion;
9. A device which is capable of generating different outputs where the output is not a direct ratio of input; and
10. A compound mechanism, such as a differential, with two inputs and one output.
An important object of this invention is to provide a mechanical movement which includes a shaft, a frame surrounding the shaft and having a plurality of supporting surfaces which are equally spaced from the shaft and from each other, rockers interposed between each of the supporting surfaces and the shaft, and flexible motion-transmitting band means secured under tension to and extending between a pair of the supporting surfaces wherein the band means is arranged to partially encompass the shaft and the rockers interposed between each of said pair of supporting surfaces and the shaft in a generally sinuous fashion.
Another object of this invention is to provide a mechanical movement of the type described which can be utilized in an airspeed indicator.
Other objects, features and advantages of the invention will be apparent from the following description of the invention taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective partially diagrammatic view of an airspeed indicator incorporating one embodiment of the invention;
FIG. 2 is an end view and FIG. 3 is a side view of the mechanical movement per se shown in FIG. 1 which includes all of the major components thereof;
FIGS. 4, 5 and 6 are sectional views taken substantially along lines 4-4, 5-5 and 6-6, respectively, of FIG. 3;
FIG. 7 is a stretchout view of a one-piece construction of the flex band;
FIG. 8 is a diagrammatic view of the airspeed indicator shown in FIG. 1;
FIG. 9 is a diagrammatic view showing another embodiment of the mechanism shown in FIG 8;
FIG. 10 is a sectional view showing another embodiment of the invention in which the device can function as a compound mechanism such as a differential;
FIG. 11 is a diagrammatic end view of the mechanism shown in FIG. 10; and
FIGS. 12 and 13 show a sectional end view, respectively, of a still further embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 it will be seen that the airspeed indicator includes a fixed axis rotary mechanism, indicated generally by the numeral 10, which is driven by a differential pressure diaphragm 12 through a rigid link 14 for controlling movement of the indicator pointer 16. All of the foregoing components are mounted within a housing 18. The housing 18 includes end plates 20, as shown in FIGS. 2 and 3, to which three supporting frame members 22, 24 and 26 are suitably secured. In this embodiment the frame members are fixed and do not move during the operation of the device. Three conjointly movable rocker members 28, 30 and 32 are interposed between a center shaft member 34 and the supporting surfaces of the frame members. A flexible band 36, which is of a continuous single-piece construction, interconnects the frame members, rocker members, and center shaft member in the manner illustrated in FIGS. 4, 5 and 6. More specifically, the flexible band is in effect formed of three segments or sections 36a, 36b, 360, as shown in FIG. 7. Each section is secured to its associated frame by a clamp 38 and to the rockers with pins 40. Tautness or tension is maintained in each band through use of springs 42. Each flexible band section serves to align and constrain the motion of two adjacent rockers. FIGS. 3 and 7 illustrate how band sections 360 and 36b are divided into two strips which are positioned symmetrically on each side of 360. Such an arrangement is necessary in order to balance the constraining forces on the rockers. Although FIG. 7 which is a stretchout view of band 36, illustrates how this band can be constructed as one continuous piece, it will be understood that, if desired, three separate bands could be utilized to accomplish the same purpose. Pin holes 44, which appear in FIG. 7, are utilized for attaching the bands to the rockers, and band spurs 36d with pin holes 46 are utilized for attaching the band to the shaft 34.
Referring specifically to FIG. 3 and FIGS. 4-6, it will be seen that the three band sections 36a, 36b and 36c are positioned so that band section 36a is secured to frame members 22 and 26 and is arranged to partially encompass the shaft member 34 and the rocker members 28 and 32 in a generally sinuous fashion; band section 36b is secured to frame members 26 and 24 and is arranged to partially encompass the shaft member 34 and the rocker members 32 and 30 in a generally sinuous fashion; and band section 36c is secured to frame members 24 and 22 and is arranged to partially encompass the shaft member 34 and the rocker members 30 and 28 in a generally sinuous fashion.
The fixed axis rotary device which is disclosed herein is similar to a roller bearing to the extent that the frame serves as an outer shell or race of a bearing, and the rockers function as rolling elements which support the shaft. Significant differences are found, however, in the configuration of the components, in the limited rotation of the shaft, and in the use of flex bands instead of a roller retainer. The components are configured in such a manner that contact is retained with the shaft as the rockers roll across the frame surfaces, as shown in FIG. 2. The flex band sections are pinned, clamped or otherwise secured to the frame, rockers and shaft. In this manner the rockers are aligned between the frame and shaft and the motion of components are constrained to permit rolling without sliding. The inherent lateral stiffness of the flex band prevents any axial movement of the shaft and rockers relative to the frame. Because no sliding action occurs, operating clearance is not necessary and lubricants are not required. There are no random surface contacts, and rolling friction from small surface irregularities decreases as mating surfaces conform to these irregularities. Radial clearance is minimized or eliminated by radial adjustment of the frame members 22, 24 and 26. The wide support provided by these frame members enables a singledevice to be used with shafts having overhanging loads. Interconnecting all components with a taut flex band eliminates lost motion.
Bias torsional spring forces are controlled by the band segment widths 36a, 36b, and 36c. If each bandwidth is constant, there is no bias spring force because the elastic strain energy is balanced. If the width of a band segment is greater at one rocker contact point than at the other rocker contact point, a bias spring force will exist tending to force the device to a state of less internal strain energy. FIG. 7 illustrates an alternate contour 36c which will provide a constant bias spring force. It will be understood by those skilled in the art that various types of contours can provide positive, negative, or step torquedeflection relationships.
The foregoing described fixed axis rotary device is especially suited for instrument mechanisms such as an airspeed indicator. Prior art airspeed mechanisms have consisted of a pressure-sensing diaphragm and link, rocking shaft arm and pin, rocking shaft with jewel bearings, pointer shaft with jewel bearings, gear drive between the shafts, and a torsion spring for elimination of lost motion.
Referring to FIG. 1 and FIG. 8, which is a diagrammatic view of the airspeed indicator shown in FIG. 1, it will be seen that the diaphragm 12 is connected to the rocker 28 through means of a rigid link 14 and pin 50. Movement of the diaphragmis magnified by the linkage and is displayed by the pointer 16 attached to the center shaft 34. The characteristic deflection curve of the diaphragm can be modified by the mechanism to suit the design requirements. This is accomplished by changing the rocker profile and, if necessary, the shaft and frame member profiles.
For diaphragm pressure sensors of limited travel, the motion can be magnified to almost any degree for a given device. For example, referring to FIG. 8, it can be seen that the equation B indicates the relationship between the angular shaft motion and the horizontal pin displacement x. As dimension A approaches zero, the ratio approaches infinity. In the foregoing equation:
0 =the angular movement of the center shaft;
B the distance between the contact points of the rocker with the shaft and frame; R the radius of the center shaft; A the distance between the pin 50 and the supporting surface of the frame; and
x the horizontal pin displacement In the alternate embodiment, which is shown in FIG. 9, the rigid link 14 and pin 50 arrangement is replaced by a flex band 52 which is secured at one end to a cam 54 on rocker 28 and at the other end to the diaphragm. The flex band 52 is kept taut by loading the diaphragm against a bias spring force generated by the band sections of flex band 36. The embodiment shown in FIG. 9 permits maximum amplification of diaphragm movement by minimizing dimension A throughout the operating range of the device.
If the frame of the device described herein is allowed to rotate, the device can be made to function as a compound mechanism such as a differential. Thus, referring to FIGS. 10 and 11 wherein like parts are designated by like numerals plus 100, it will be seen that the center shaft 134 is mounted on suitable bearings 60 and that a unitary frame or housing 118, which includes three supporting surfaces or members 122, I24 and 126 is allowed to rotate. All three of the basic components, that is, the frame 118, the rocker 28, and shaft 134 which are interconnected by flex band sections in the same manner previously described, are provided with input/output means such as gears 62, 64, and linkage 66. With such an arrangement it is possible to accommodate inputs and outputs without separate components, that is, without the necessity of using separate drives for input and output as in a planetary gear differential. Furthermore, the low friction of the device permits operation thereof with low input forces.
FIGS. 12 and 13 show a further embodiment of the invention wherein like parts are designated by like numerals plus 200. In this embodiment circular rockers 228, 230 and 232 are utilized in conjunction with a noncircular shaft 234. Although the device is shown within a unitary frame housing 218 having supporting surfaces 222, 224, and 226 it will be understood that the frame could also be of a nonunitary construction. The frame, rockers, and shaft are interconnected by flex band sections in essentially the same manner as was previously described. With this arrangement it will be apparent that the angular movement of the noncircular shaft 234 will be considerably less than in the previous arrangements where a circular shaft is utilized.
The several practical advantages which flow from this invention are believed to be obvious from the foregoing description, and other advantages may suggest themselves to those who are familiar with the art to which this invention relates.
Furthermore, although this invention has been described in connection with various specific embodiments, it will be obvious to those skilled in the art that various changes may be made in the form, structure, and arrangement of parts without departing from the spirit of the invention.
Having thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is:
l. A device of the class described, comprising a rotatable shaft member, a plurality of supporting members spaced from said shaft member and from each other, a plurality of conjointly movable rocker members, one of which is interposed between each of said supporting members and said shaft member, and flexible motion-transmitting band means secured under tension to and extending between a pair of supporting members, said band means being arranged to partially encompass said shaft member and the rocker members interposed between each of said pair of supporting members and said shaft member in a generally sinuous fashion.
2. The structure, as defined in claim 1, wherein each of said rocker members includes a surface which mates with a surface on the supporting member associated therewith.
3. The structure, as defined in claim 2, wherein one of the mating surfaces of said rocker and supporting members is convex.
4. The structure, as defined in claim 3, wherein the other of the mating surfaces of said rocker and supporting members is flat.
5. The structure, as defined in claim 1, wherein each of said rocker members includes two surfaces, one of which mates with a surface on said shaft member and and the other of which mates with a surface on the supporting member associated therewith.
6. The structure, as defined in claim 5, wherein both of the mating surfaces of each rocker member are convex.
7. The structure, as defined in claim 1, wherein said supporting members are spaced from said shaft member and from each other.
8. The structure, as defined in claim 7, wherein said band means is secured to and extends between each pair of adjacent supporting members.
9. The structure, as defined in claim 8, which includes first, second, and third supporting members and first, second, and third rocker members.
10. The structure, as defined in claim 9, wherein said band means comprises fist, second, and third band sections, the first of which is secured to said first and second supporting mem bers and is arranged to partially encompass said shaft member and said first and second rocker members in a generally sinuous fashion, the second of which is secured to said second and third supporting members and is arranged to partially encompass said shaft member and said second and third rocker members in a generally sinuous fashion, and the third of which is secured to said third and first supporting members and is ar ranged to partially encompass said shaft member and said third and first rocker members in a generally sinuous fashion.
11. The structure, as defined in claim 10, wherein said band means is a continuous single piece construction which in cludes said three sections.
12. The structure, as defined in claim 11, wherein said first band section comprises a first strip for aligning and constraining the motion of said first and second rocker members, said second band section comprises second and third strips which are symmetrically spaced from said first strip for aligning and constraining the motion of said second and third rocker mem bers, and said third band section comprises fourth and fifth strips which are symmetrically spaced from said first strip and from said second and third strips for aligning and constraining the motion of said third and first rocker members.
13. The structure, as defined in claim 12, which includes resilient means operatively connected to each of said supporting members and the band section secured thereto for maintaining said band section under tension.
14. The structure, as defined in claim 13, which includes input means operatively connected to one of said rocker members for causing conjoint rolling of all of said rocker members on said support members and consequent rotation of said shaft member about a fixed axis.
15. The structure, as defined in claim 14, which includes stop means on said rocker members for limiting rotation of said shaft member.
16. A device of the class described, comprising shaft means, frame means surrounding said shaft means and having a plurality of supporting surfaces spaced from said shaft means and from each other, rocker means interposed between each of said supporting surfaces and said shaft means, and flexible motion-transmitting band means secured under tension to and extending between a pair of said supporting surfaces, said band means being arranged to partially encompass said shaft means and the rocker means interposed between each of said pair of supporting surfaces and said shaft means in a generally sinuous fashion.
17. The structure, as defined in claim 16, wherein said frame means is fixed and said shaft means is rotatable about a fixed axis.
18. The structure, as defined in claim 16, wherein said shaft means is fixed and said frame means is rotatable about a fixed axis.
19. The structure, as defined in claim 16, wherein said shaft means is rotatable about a fixed axis and said frame means is rotatable about a fixed axis.
20. The structure, as defined in claim 16, wherein said rocker means includes a plurality of conjointly movable rocker members, one of which is interposed between each of said supporting surfaces and said shaft means.
21. The structure, as defined in claim 20, wherein said shaft means is a shaft member having a circular cross section and said rocker members have a noncircular cross section.
22. The structure, as defined in claim 20, wherein said shaft means is a shaft member having a noncircular cross section and said rocker members have a circular cross section.