CA1169669A - Resilient rotary coupling - Google Patents
Resilient rotary couplingInfo
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- CA1169669A CA1169669A CA000383153A CA383153A CA1169669A CA 1169669 A CA1169669 A CA 1169669A CA 000383153 A CA000383153 A CA 000383153A CA 383153 A CA383153 A CA 383153A CA 1169669 A CA1169669 A CA 1169669A
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Abstract
ABSTRACT
RESILIENT ROTARY COUPLING
A resilient rotary coupling 10 and a marine drive 18 including same are described. The coupling 10 includes inner and outer rotary members 14,12, respectively. The inner sur-face 18 of the outer rotary member 12 and the periphery 26 of the inner member 14 are of similar configuration and include, when viewed in cross section, at least two arcs of greater radius of curvature symmetrically disposed about the axis of rotation 23 connected in alternate manner by an equal number of arcs of lesser radius of curvature, the arcs of greater radius of curvature being located closer to the axis of rotation 23 than the arcs of lesser radius of curvature, the center of curvature of each of said arcs lying on or within the boundary of the closed figure defined by the inner surface 18 in said section. The arcs are connected to one another without any abrupt change of radius or radius of curvature. Resilient means 17 are disposed between the outer and inner rotary members 12,14, respectively. The resilient means 17 is in radial com-pression and contacts completely in the circumferential direction of the members 12,14 at least a portion of the inner surface 18 of the outer member 12 and the periphery 26 of the inner member 14. The coupling 10 may be designed so as to permit slippage upon application of loads in excess of design or to permit torsional shock absorption up to a maximum torque load at which time the inner and outer rotary members 14,12, respectively mechanically lock up relative to one another thereby preventing further angular displacement of them relative to one another.
RESILIENT ROTARY COUPLING
A resilient rotary coupling 10 and a marine drive 18 including same are described. The coupling 10 includes inner and outer rotary members 14,12, respectively. The inner sur-face 18 of the outer rotary member 12 and the periphery 26 of the inner member 14 are of similar configuration and include, when viewed in cross section, at least two arcs of greater radius of curvature symmetrically disposed about the axis of rotation 23 connected in alternate manner by an equal number of arcs of lesser radius of curvature, the arcs of greater radius of curvature being located closer to the axis of rotation 23 than the arcs of lesser radius of curvature, the center of curvature of each of said arcs lying on or within the boundary of the closed figure defined by the inner surface 18 in said section. The arcs are connected to one another without any abrupt change of radius or radius of curvature. Resilient means 17 are disposed between the outer and inner rotary members 12,14, respectively. The resilient means 17 is in radial com-pression and contacts completely in the circumferential direction of the members 12,14 at least a portion of the inner surface 18 of the outer member 12 and the periphery 26 of the inner member 14. The coupling 10 may be designed so as to permit slippage upon application of loads in excess of design or to permit torsional shock absorption up to a maximum torque load at which time the inner and outer rotary members 14,12, respectively mechanically lock up relative to one another thereby preventing further angular displacement of them relative to one another.
Description
~ 169669 , RESILIENT ROTARY COUPLING
The abstract is not to be taken as limitina the invention of this application and in order to understand the full nature and extent of the technical disclosure of this application, reference must be made to the accom-panying drawing and the following detailed description.
The invention pertains to a resilient rotary coupling. The coupling is particularly suited for use in a marine propeller drive, although it is not intended that the invention be limited to such application.
The need for torsional shock and vibration absorption between the propeller drive shaft and the propeller has long been recognized. Many arrangements have been proposed.
~5 Various aspects of this invention are as follows:
In a marine propeller drive having a propeller and propeller drive shaft, the improvement of a resilient, indexing, rotary marine drive coupling having an axis of rotation and being for coupling the propeller and the propeller drive shaft of the marine drive, the coupling comprising: (a) an outer rotary member having an axially elongated inner surface which in section taken perpendicularly to said axis includes at least two arcs of greater radius of curvature symmetrically disposed about said axis connected in alternate manner by an equal number of arcs of lesser radius of curvature, said arcs of greater radius of curvature being located closer to said axis than said arcs of lesser radius of curvature, the center of 2 curvature of each of said arcs lying on or within the boundary of the closed figure defined by said inner surface in said section and the arcs being connected to one another without any abrupt change of radius or radius of curvature, (b) an inner rotary member having ~ 169~
an axially elongated periphery opposing the inner surface of said outer member, said periphery being of a cross-sectional configuration generally corresponding and complementary to that of the inner surface of said outer member but being of lesser radial dimensions such that the periphery of said inner member is spaced radiallv from the inner surface of said outer member when each is centered on said axis and no load is imposed on the coupling, and (c) resilient elastomeric means disposed between said outer and inner members, said resilient means being in radial compression and contacting completely in the circumferential direction ~ of said coupling at least a portion of each of said inner surface and said periphery, (d) in which the corresponding arcs of lesser radius of curva~ure of the inner and outer members are generally aligned when there is no load imposed on the coupling, and (e) in which the radial distance from the axis of the arcs of lesser radius of curvature of the inner member i8 less than the radial distance from the axis of the arcs of greater radius of curvature of the outer member and thereby provides permanent rotary displacement of the inner member relative to the outer member.
In a marine propeller drive having a propeller and propeller drive shaft, a resilient, indexing, rotary marine drive coupling having an axis of rotation and being for coupling the propeller and the propeller drive shaft of the marine drive, the coupling comprising: (a) an outer rotary member having an axially elongated inner surface of generally square cross-sectional configuration comprising a series of four chordally disposed flat areas connected by rounded corners disposed a great radial distance from said axis than the radial distance of bi-secting radius normal to said flat areas, the circumferentially measured arc length of each rounded corner being at least equal to - 1 lB966~
the circumferentially measured dimension of each flat.
area, (b) an inner rotary member comprising a metallic bushing adapted to be received on and matingly engage a shaft, said inner member having an axially elongated periphery opposing the inner surface of said outer member, said periphery being of generally square cross-sectional configuration generally corresponding and complementary to that of the inner surface of said outer member but being of lesser radial dimensions such that the periphery of said inner member is spaced radially inwardly from the inner surface of said outer member when each is centered on said axis and no load is imposed on the coupling, and (c) resilient elastomeric means o~ vulcanized rubber disposed between said outer and inner members and bonded to said inner member, said resilient means being approximately equally radially compressed throughout itQ
circumferential and axial extent between said inner surface and said periphery and contacting compLetely in the circumferential direction of said coupling at least a portion of each of said inner surface and said periphery, the amount of compression being about 35 percent upon assembly of the coupling and about 60 percent when the inner member and outer member are angularly displaced such that the corners of the inner member are nearest the f].at areas of the inner surface of the outer member, (d) in which the corresponding flat areas of the outer and inner members are generally parallel and symmetrically disposed about said axis when there is no load imposed on the coupling, and (e) in which the radial distance from the axis of the rounded corners of the inner member is less than the radial distance of the bi-secting radius of the outer member and thereby provides permanent rotary displacement of the inner member relative to the outer member.
~ 169669 In the drawing:
Figure 1 is a side elevation partially in section of a portion of a marine drive according to an embodiment of the invention;
Figure 2 is a fragmentary cross-sectional view taken perpendicular to the axis of rotation of the coupling along line II-II of Figure l;
Figure 3 is a fragmentary cross-sectional view taken parallel to the axis of rotation of the coupling along line III-III of Figure l;
Figure 4 is an end view of the inner member and resilient means shown in Figures 2 and 3;
Figure 5 is a cross-sectional view taken along lines V-V of Figure 4;
Figure 6 is a cross-sectional view taken perpendicular to the axis of rotation of another embodiment of a coupling according to the invention; and Figure 7 is a cross-sectional view taken per-pendicular to the axis of rotation of another embodiment of a coupling according to the invention.
Referring to Figure 1 there is shown a portion of a marine drive 8 including a resilient rotary coupling 10 according to an embodiment of the invention coupling a ~haft 24 to a marine propeller 11.
Referring to Figure~ 2 and 3 there is shown an embodiment of a resilient rotary coupling 10 according to the invention as applied to a marine propeller drive installation. The resilient rotary coupling 10 includes an outer rotary member 12 shown as an example as propeller hub 13, an inner rotary member 14 shown as an example as bushing 15, o~ complementary configuration and resilient means 17 disposed between the outer and inner members.
The outer rotary member 12 includes an axially elongated inner surface 18 of polygonal cross section.
As illustrated in Figure 2 the lnner surface 18 of the propeller hub 13 includes four chordally di~posed flat areas 20 with the adjacent ones of the flat areas connected to one another by rounded corners 22. The rounded corners 22 are disposed a greater radial dlstance R from the axis of rotation 23 of the re~ilient rotary coupling 10 than the radial distance r of a bi-secting radius normal to said flat areas 20. Mathematically expressed, R/r~ 1.
While the outer rotary member 12 illustrated is a marine propeller, or more particularly, the hub 13 of a marine propeller, it is to be understood that such outer rotary member could be any suitable driving or driven member in a machine arrangement.
The resilient rotary coupling 10 also includes an inner rotary member 14 which in the examples shown is a metallic bushing 15 having a configured bore 16 for mating engagement with the propeller drive shaft 24. me inner rotary member 14 includes an axially elongated periphery 26 in confronting or opposing relationship to the inner surface 18 of the hub 13 of the propeller 11. me per-iphery 26 of the inner member 14 i8 of polygonal cross section generally corresponding and complementary to that of the inner surface 18 of the outer member 12.
As shown in Figures 2 and 3, the periphery 26 of the bushing 15 i~ of lesser radial dimensions than those of the inner surface 18 of the propeller hub 13, In other words the periphery 26 of the bushing 15 is spaced radially inwardly toward the axis of rotation from the inner surface 18 of the outer member 12 when each is centered on the axis of rotation 23 of the coupling 10 and no load is imposed.
It is to be understood that the inner member 14 could alternately be formed so as to be an integral iart of the drive shaft 24 or could itself be the driven member rather than the driving member of the coupling.
The coupling 10 also includes resilient means 17 disposed between the outer member 12 and inner member 14.
The resilient means 17 is in radial compression even when no load or torque is applied or being transmitted through the coupling 10. The resilient means 17 is brought into lnitial radial compression upon assembly of the coupling 10. The resilient means 17 contacts completely in the circumferential direction of the coupling 10 at least a portion of ~aid axially elongated inner surface 18 of the outer member 12 and the axially elongated periphery 26 of the inner member 14.
When viewed in the CrosS section shown in Figure 2, the resilient means 17 contacts all of the periphery 26 of the bushing 15. In this cross-section, the periphery 28 of the resilient means 17 is itself contacted by all of the inner surface 18 of the outer member 12. As shown in Figures 2 and 3, there are no void~ between the oppo~ed .working curfaces 26, 18 of the inner and outer members since this space i~ occupied completely by the resilient means 17. The resilient means 17 is prefenably contlnuous in the circumferential direction of the coupling 10 and bonded to one of the respective inner or outer rotary 35- members 14,12. It is most preferable that the resilient means 17 be bonded to the inner rotary member 14 such as .SU. 169~69 to bushing 15 illustrated in Figures 1 through 5.
The resilient means 17 is formed of an elastic polymeric material and is preferably made of natural rubber, or of a synthetic polyisoprene blended with styrene butadiene rubber. When rubber is used for the resilient means, it should be compounded to a durometer of about 75 to 80 Shore A Hardness and be high in tear strength and adhesion as measured on a peel-type strip test such as ASTM D429, Method B. Compression set should be as low as obtainable while maintain~ng the above given properties and preferably should not exceed 25 to 30%
when measured according to ASTM D395, Method B, for 22 hours at about 158F. It is believed that other elasto-meric materials may be satisfactory in this application, including polyurethane. Specific formulations are not presented herein as suitable formulations are known or readily developed by those skilled in the art.
The undeformed configuration o~ a preferred embodl-ment of the resilient means 17 is shown in Figures 4 and 5 in which the bushing 15 of the coupling 10 qhown in Figures 1, 2 and 3 is illustrated including in its as-manufactured, undeformed state the resilient mean~l7 of vulcanized rubber of thickness T bonded to the central portion 32 of its periphery 26. The thickness T of the resilient means 17 as measured along a radius extending perpendicularly from the axis of rotation 23 of the - bushing 15 is i~ a preferred embodiment reduced about - 35% upon installation of the bushing 15 with the resilient means 17 bonded thereto into the outer member 12. The configuration of, the outer member 12 and the bushing 15 are prefer~bly chosen such that the resilient means 17 is further compressed at maximum torsional load to about 60% of its original undeformed radial dimension.
In oth~r words, ~hen the corner~ 30 of the inner member 14 are nearest the flat areas 20 of the outer member 12, ~ 169669 the resilient means 17 is compressed about 60% in the radial direction at those areas.
Because the resilfent means 17 undergoes considerable radial compression upon assembly of the coupling 10 the resilient elastomeric means in its undeformed, as-manufactured state is preferably of considerably greater radial dimension and lesser axial dimension than in the assembled coupling. In this regard compare Figure 5 with Figure 3. For this reason the resilient means 17 preferably in its undeformed state contacts and is bonded to the central portion 32 of the periphery 26 of the bushing 15 and is of generally unifbrm thickness T
throughout both its circumferential and axial extent in central portion 32. The resilient means 17 preferably has radiused corners 34-which extend about its circum-ference at its axial extremities and fillets 35 at its junction with the periphery 26 of bushing 15 to reduce stresses at these locations. These stresses are particu-larly high during assembly of the coupling 10. The bushing 15 includes an internal bore 16 for mating en-gagement with a drive shaft such as propeller shaft 24 shown in Figures 1, 2 and 3.
Referring now to Figure 6 there is illustrated another embodiment according to the invention of a rotary coupling 37. The periphery 40 of the inner member 38 when viewed from the end or in a cross section taken normal to the - axis of rotation 41 of the inner member 38 is of generally elliptical configuration. It is believed that the ratio of the major axis to minor axis should be in the range 3 of 1.05 to 1.15 to obtain maximum angular displacement of the inner member 38 and outer member 39 relative to each other without seriously damaging the rubber of resilient means 42 when it is subjected to maximum impact torsional loading. This design permits a full 90 angular displac~ment before the resilient means 42 is sub~ected ~ 169~69 to its maximum radial compression whereas in the embodiment illustrated in Figures 1-5 the resilient means 17 is sub-~ected to its maximum radial compression at 45 displace-ment of the inner member 14 relative to the outer member 5 12. In the embodiment illustrated in Figure 6 the outer rotary member 39 includes an axially elongated inner surface 43 which in a section taken perpendicularly to the axis of rotation 41 includes two arcs 44 of greater radius of curvature which are diametrically opposed from one another. These arcs 44 are connected in alternate manner by two arcs 45 of lesser radius of curvature which are also diametrically opposed from one another. The arcs 44 of greater radius of curvature are located closer to the axis of rotation 41 than the arcs 45 of lesser radius of curvature. As with the embodiments already discussed, the periphery 40 of the inner rotary member 38 opposes the inner surface 46 of the outer member 39. The periphery 40 of the inner member 38 is of a configuration generally corresponding and complementary to that of the lnner surface 46 of the outer member 39 but is of lesser radial dimensions such that the periphery 40 of the inner member 38 is spaced radially fr~m the inner surface of the outer member when each is centered on the axis of rotation 41 and no load is imposed on the coupling.
This spacing need not be exactly equal throughout the circumferential direction. The periphery 40 of the inner member 38 may be mathematically specified and the inner surface 46 of the outer member 39 constructed there-from or mathematically specified. When both are mathematic-ly specified as true elipses, the distance betweenthem will not be a true constant at all polnts. This non-uniformity is believed not to adversely affect the coupling and may provide a means for tuning the torsional load versus angular deflection characteristics of the coupling. Resilien~t elastomeric means 42 is dis-posed between the inner and outer members. The resilient ~ 1~95~9 means 42 is in radial compression and contacts completely in a circumferential direction of the coupling the inner working surface 46 of the outer member 39 and the working periphery 40 of the inner member 38. When no load is 5 imposed on the coupling the corresponding arcs 44,47 of lesser radius of curvature of the outer and inner members are generally aligned. When a torsional load is imposed on the coupling these corresponding areas 44,47 of lesser radius of curvature are angularly displaced relative to one another thus increasing the amount of compression of the resilient means 42 adjacent the arcs 49 of lesser radius curvature of the inner rotary member 38. The resilient means 42 is compressed about 35% from its un-deformed configuration upon assembly of the coupling 37, 15 The periphery 48 of the resilient means 42 before being compressed is shown by dashed lines in Figure 6. The resilient member 42 is of approximately even thickness throughout and is approximately evenly compressed through-out upon assembly of the coupling 37.
In Figure 7 there is shown yet another embodiment of a coupling 50 according to the invention. The outer rotary member 51 includes an axially elongated inner surface 52 which in a section taken perpendicularly to the axis of rotation 53 includes three arcs 54 of greater 25 radius of curvature symmetrically disposed about the axis of rotation 53. The arcs 54 of greater radius o~ curvature are connected in alternate manner by an equal number of arcs 55 of lesser radius of curvature which are also symmetrically disposed about the axis of rotation 53.
The arcs 54 of greater radius or curvature are located closer to the axis of rotation 53 than the arcs 55 of lesser radius of curvature. The center of curvature of each of said arcs lies within the outer boundary of the section of the inner surface 52. The arcs 54,55 are connected 35 to one another without any abrupt change of radius or ~ 169869 of radiu~ of curvature. The configuration depicted in Figure 7 may be called tri-oval. As in the other em-bodlment~ ~hown the resilient means 56 is of sub~tan-tially even thickness throughout between the inner surface 52 of outer member 51 and the periphery 57 of inner member 58 and is ~ub~tantially evenly compres ed upon as~embly o~ the coupling 50. The inner and outer f rotary members are of complementary configuration. The arcs 59 of lesser radius of curvature of the inner rotary member 58 are generally aligned with the arcs 55 of les~er radius of curvature of the outer rotary member when no load is impo~ed onto the coupling and are angularly displaced relative to one another upon impo~ition of a torsional load, thus increasing compression oi the resilient means 56.
A coupling according to the present invention can be designed so as to permit permanent angular displacement or, in other words, rotary slip, ratcheting or indexing or the inner and outer members relative to one another.
In the embodiment ~hown in Figures 1-5 if rotary slip at a predetermined torque is desired the radial distance P from the axis of rotation 23 of the rounded corner~ 30 of the inner member 14 mu~t be le~s than the radial di~-tance r of a bisecting radiu~ normal to the flat areaq 20 of the outer member 12. Expres~ed mathematically, P~ r.
Referring to Figure 6, i~ rotary slip at a predetermined torque is desired the radial distance from the axis of ro-tation 41 of the arc 49 of les~er radius of curvature of the inner member 38 mu~t be le3s than the radlal distance of the arc 44 of greater radiu~ of curvature of the outer member 39.
On the other hand, if it is desired to provide limited angular displacement between the inner and outer rotary members of a coupling according to the invention, this too, can be provided by design choice o~ the relative dimensions of the inner and outer rotary members. For g~69 example, in the embodiment shown in Figures 1-5 the radial distance P from the axis of rotation 23 of the rounded corners 30 o~ the inner member 14 would be es-tablished greater than the radial distance r of a bi-secting radius normal to the flat areas 20 of the outermember 12. Expre~sed mathematically, P~ r. When this relationship exists, upon ~u~fic~ent angular or rotary deflection or displacement of the rounded corners 30 of the inner member 14 relative to those of the outer member 12 the rounded corners 30 of the inner member 14 come into contact with the flat areas 20 of the correspondingly configured outer member 12 and prevent any further angular displacement of the members 12 and 14 relative to one another, Because the resilient means is not fluid, lockup will occur at some value of P~ r, provided the torque load does not càuse total failure of the re~ilient means through exce~sive shearing. At displacements below that at which mechanical loc~up occurs the resilient ela8tomeric means 17 cushions any torque loadlng between the inner member 14 and outer member 12, In similar fashion the dimensions of the inner and outer members in the embodi-ment shown in Figures 6 and 7 can be establi~hed such that upon sufficient angular or rotary deflection of the inner and outer members relative to one another the arcs of lesser radius of curvature of the inner rotary member will come into contact or interference with the arcs of greater radius of curvature of the outer rotary member to prevent further angular displacement of the inner and outer rotary members relative to one another.
It is believed that the radial distance between the inner surface of the outer member and the periphery of the inner member should be established such that the resilient means when ~ormed of rubber is compres~ed about 35% upon assembly of the coupling. Because the inner and outer rotary members are of generally corres-ponding and complementary cross-sectional oonfiguration ~169669 _ 13 -the resilient means is approximately compressed uniformly about the circumference of the coupling. In a preferred high t~rque capability embodiment of the coupling similar to that shown in Figu~es 1-5 the radial distance between the inner surface 18 of the outer member 12 and the periphery 26 of the inner member 14 as well as the radial distance p of the corners 30 of the inner member 14 in comparison to the radial distance r of bisectine radlus normal to the flat areas 20 was chosen such that when the inner member 14 and the outer member 12 are angularly displaced relative to one another so that the corners 30 of the inner member 14 are nearest the flat area 20 of - the inner surface 18 of the outer member 12 the resilient means 17 is compre8sed to about 60% of its new undeformed configuration. It is believed that when rubber is used for the resilient means that maximum radial compression should be restricted to about 60%. An exception to this guideline, of course, exists when the member~ of the coupling are dimensioned 9uch that lnterference of the periphery of the inner member and the inner suriace of the outer member will occur upon sufficient angular deflection.
It ha~ already been explained that the coupling can be designed so as to permit angular slip between its 25 inner and outer members or to be of a lock-up or non-slipping type design. The radius of the corners 30 or areas of smaller radius of curvature on the inner member 14 also have an effect on torque characteristics and the life of the coupling 10 and particularly on the llfe of the intermediate resilient means 17. If the corner~ 30 of the inner member 14 are sharper, that is, of a smaller radius of curvature, when all other factors are equal, it is more likely that the resilient means 17 may become cut, torn or ruptured. It is thus preferable that the circumferential arc length 62 of each rounded corner 30 oi the inner member or arc of lesser radius oi curvature be at least equal to the circumferential dimension 63 of each flat area 64 or arc of greater radius of curva-ture of the inner member 14. It i~ most preferable that the circumferential arc length of each rounded corner 30 or arc of lesser radius of curvature of the inner member be at least 150% of the circumferential dimension of each flat area 20 or area of greater radius of curvature of the respective inner member. In the embodiment shown - in Figures 1-5, which is a preferred embodiment, the cir-cumferential arc length of each rounded corner is equal to or greater than the circumferential dimension of the corresponding flat area of the respective inner member 14, outer member 12 or resilient means 17.
In the embodiment illustrated in Figures 1-5, the periphery 26 of the inner member 14, the inner surface 18 of the outer member 12, and the resilient means 17 are each of generally square cross-sectional configuration and include four flat areas connected by rounded corners and are of generally uniform size throughout the axial extent of the confronting surfaces. No taper in the direction of the axis of rotation is required in a coupling according to the invention, although such taper may be employed to ease a~sembly and disassembly of the coupling.
When used in a marine drive, the coupling i~ removed as a unit from the propeller shaft. The coupling itself is not intended to be serviced in the field due to press fitting of the inner member into the outer member with attendant compression of the resilient means.
The configuration of the inner and outer members and the resilient means have been described to be poly-gonal or polyoval. The minimum number of flat area~, i.e., areas of greater radius of curvature is two and this will usually by employed in a lock-up type design having a limited angular deflection between the inner and outer members of the coupling. All el~e belng held ~966 constant, as the number of flat areas on the inner and outer members is increased it becomes easier to cause the inner and outer members to slip rotationally relative to one another. As the number of flat areas on the inner and outer members is increa~ed the angular displacement between the inner and outer members prior to permanent slip or angular displacement of these members relative to one another is lowered as is the maximum torque transmission capability o~ the coupling for a given over-all physical size, similar compounding for the resilientmeans, and same degree of precompression of the resilient means upon assembly of the coupling. It is believed that about eight flat areas on the inner and outer members are a practical maximum number, It is to be noted that the configuration of the inner and outer members does not have to be that of a regular polygon having rounded corners as illustrated but rather can be rectangular ~ith rounded corners or elliptical, tri-oval or polyoval. A
configuration whi¢h is symmetrlcal about the axis of rotation of the coupling however is preferred to avoid radial displacement of the inner or outer members relative to the axis of rotation upon application of a torque load.
In preferred embodiments, the resilient means is formed of wlcanized rubber and is sized so as to be subjected to substantially equal radial compression at all points about its circumference upon assembly of the inner and outer members to form a coupling of the invention. Increasing the amount of radial compression of the resilient means upon assembly of the coupling will increa~e the torsional spring rate and maximum torque capability of the coupling, all else being equal and vice versa. Preferably the resilient means is adhered to the inner member and has a relatively high adhesion, for exàmple, about 50 pounds per inch width as measured by ; 35 cutting the resilient means and allowing the part to g 16~6~9 roll and thereby peeling the resilient means from the inner member.
The resilient means is preferably molded and bonded to the inner member. Transfer or injection molding are preferred over compression molding since the latter is not believed to be as accurate. It is desired that concentricity of the inner and outer members be maintained and therefore an accurate molding process for evenly forming the resilient means about the inner member is desirable.
The term "axially" and related terms as used herein mean in the direction of or parallel to the axis of rotation of the coupling or that of any of its constituent elements such as the inner member, the resilient means, or the outer member as herein described. The term "radially"
and related terms as used herein mean in a plane inter- -secting the axis of rotation and perpendicular to the axis of rotation as defined hereln, The term "circum-ferentially" and related term~ as used herein mean in a directlon around the axls of rotation as defined herein.
The term "arc" and related terms as used herein mean a curved line or any section of a curve and are not to be limited to a constant radius of curva~,ure but are in-tended to include a continuously changing radius of curvature.
The term "polyoval" as used herein refers to a closed two dimensional figure all of whose boundary portions are straight or curved such that the center of radius of curvature of all points of the boundary lie on or within the figure. An example of a polyoval is shown by the periphery of the inner member in Figure 7, which is a tri-oval. A coupling could, of course, be designed with a greater number of arcs of les~er radius of curvature, with about eight such areas believed to be the practical maximum, - ï7-While certain representative embodiments and details have been shown for the purpose of illustrating the ,n-vention it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing ~rom the spirit or scope of the invention.
The abstract is not to be taken as limitina the invention of this application and in order to understand the full nature and extent of the technical disclosure of this application, reference must be made to the accom-panying drawing and the following detailed description.
The invention pertains to a resilient rotary coupling. The coupling is particularly suited for use in a marine propeller drive, although it is not intended that the invention be limited to such application.
The need for torsional shock and vibration absorption between the propeller drive shaft and the propeller has long been recognized. Many arrangements have been proposed.
~5 Various aspects of this invention are as follows:
In a marine propeller drive having a propeller and propeller drive shaft, the improvement of a resilient, indexing, rotary marine drive coupling having an axis of rotation and being for coupling the propeller and the propeller drive shaft of the marine drive, the coupling comprising: (a) an outer rotary member having an axially elongated inner surface which in section taken perpendicularly to said axis includes at least two arcs of greater radius of curvature symmetrically disposed about said axis connected in alternate manner by an equal number of arcs of lesser radius of curvature, said arcs of greater radius of curvature being located closer to said axis than said arcs of lesser radius of curvature, the center of 2 curvature of each of said arcs lying on or within the boundary of the closed figure defined by said inner surface in said section and the arcs being connected to one another without any abrupt change of radius or radius of curvature, (b) an inner rotary member having ~ 169~
an axially elongated periphery opposing the inner surface of said outer member, said periphery being of a cross-sectional configuration generally corresponding and complementary to that of the inner surface of said outer member but being of lesser radial dimensions such that the periphery of said inner member is spaced radiallv from the inner surface of said outer member when each is centered on said axis and no load is imposed on the coupling, and (c) resilient elastomeric means disposed between said outer and inner members, said resilient means being in radial compression and contacting completely in the circumferential direction ~ of said coupling at least a portion of each of said inner surface and said periphery, (d) in which the corresponding arcs of lesser radius of curva~ure of the inner and outer members are generally aligned when there is no load imposed on the coupling, and (e) in which the radial distance from the axis of the arcs of lesser radius of curvature of the inner member i8 less than the radial distance from the axis of the arcs of greater radius of curvature of the outer member and thereby provides permanent rotary displacement of the inner member relative to the outer member.
In a marine propeller drive having a propeller and propeller drive shaft, a resilient, indexing, rotary marine drive coupling having an axis of rotation and being for coupling the propeller and the propeller drive shaft of the marine drive, the coupling comprising: (a) an outer rotary member having an axially elongated inner surface of generally square cross-sectional configuration comprising a series of four chordally disposed flat areas connected by rounded corners disposed a great radial distance from said axis than the radial distance of bi-secting radius normal to said flat areas, the circumferentially measured arc length of each rounded corner being at least equal to - 1 lB966~
the circumferentially measured dimension of each flat.
area, (b) an inner rotary member comprising a metallic bushing adapted to be received on and matingly engage a shaft, said inner member having an axially elongated periphery opposing the inner surface of said outer member, said periphery being of generally square cross-sectional configuration generally corresponding and complementary to that of the inner surface of said outer member but being of lesser radial dimensions such that the periphery of said inner member is spaced radially inwardly from the inner surface of said outer member when each is centered on said axis and no load is imposed on the coupling, and (c) resilient elastomeric means o~ vulcanized rubber disposed between said outer and inner members and bonded to said inner member, said resilient means being approximately equally radially compressed throughout itQ
circumferential and axial extent between said inner surface and said periphery and contacting compLetely in the circumferential direction of said coupling at least a portion of each of said inner surface and said periphery, the amount of compression being about 35 percent upon assembly of the coupling and about 60 percent when the inner member and outer member are angularly displaced such that the corners of the inner member are nearest the f].at areas of the inner surface of the outer member, (d) in which the corresponding flat areas of the outer and inner members are generally parallel and symmetrically disposed about said axis when there is no load imposed on the coupling, and (e) in which the radial distance from the axis of the rounded corners of the inner member is less than the radial distance of the bi-secting radius of the outer member and thereby provides permanent rotary displacement of the inner member relative to the outer member.
~ 169669 In the drawing:
Figure 1 is a side elevation partially in section of a portion of a marine drive according to an embodiment of the invention;
Figure 2 is a fragmentary cross-sectional view taken perpendicular to the axis of rotation of the coupling along line II-II of Figure l;
Figure 3 is a fragmentary cross-sectional view taken parallel to the axis of rotation of the coupling along line III-III of Figure l;
Figure 4 is an end view of the inner member and resilient means shown in Figures 2 and 3;
Figure 5 is a cross-sectional view taken along lines V-V of Figure 4;
Figure 6 is a cross-sectional view taken perpendicular to the axis of rotation of another embodiment of a coupling according to the invention; and Figure 7 is a cross-sectional view taken per-pendicular to the axis of rotation of another embodiment of a coupling according to the invention.
Referring to Figure 1 there is shown a portion of a marine drive 8 including a resilient rotary coupling 10 according to an embodiment of the invention coupling a ~haft 24 to a marine propeller 11.
Referring to Figure~ 2 and 3 there is shown an embodiment of a resilient rotary coupling 10 according to the invention as applied to a marine propeller drive installation. The resilient rotary coupling 10 includes an outer rotary member 12 shown as an example as propeller hub 13, an inner rotary member 14 shown as an example as bushing 15, o~ complementary configuration and resilient means 17 disposed between the outer and inner members.
The outer rotary member 12 includes an axially elongated inner surface 18 of polygonal cross section.
As illustrated in Figure 2 the lnner surface 18 of the propeller hub 13 includes four chordally di~posed flat areas 20 with the adjacent ones of the flat areas connected to one another by rounded corners 22. The rounded corners 22 are disposed a greater radial dlstance R from the axis of rotation 23 of the re~ilient rotary coupling 10 than the radial distance r of a bi-secting radius normal to said flat areas 20. Mathematically expressed, R/r~ 1.
While the outer rotary member 12 illustrated is a marine propeller, or more particularly, the hub 13 of a marine propeller, it is to be understood that such outer rotary member could be any suitable driving or driven member in a machine arrangement.
The resilient rotary coupling 10 also includes an inner rotary member 14 which in the examples shown is a metallic bushing 15 having a configured bore 16 for mating engagement with the propeller drive shaft 24. me inner rotary member 14 includes an axially elongated periphery 26 in confronting or opposing relationship to the inner surface 18 of the hub 13 of the propeller 11. me per-iphery 26 of the inner member 14 i8 of polygonal cross section generally corresponding and complementary to that of the inner surface 18 of the outer member 12.
As shown in Figures 2 and 3, the periphery 26 of the bushing 15 i~ of lesser radial dimensions than those of the inner surface 18 of the propeller hub 13, In other words the periphery 26 of the bushing 15 is spaced radially inwardly toward the axis of rotation from the inner surface 18 of the outer member 12 when each is centered on the axis of rotation 23 of the coupling 10 and no load is imposed.
It is to be understood that the inner member 14 could alternately be formed so as to be an integral iart of the drive shaft 24 or could itself be the driven member rather than the driving member of the coupling.
The coupling 10 also includes resilient means 17 disposed between the outer member 12 and inner member 14.
The resilient means 17 is in radial compression even when no load or torque is applied or being transmitted through the coupling 10. The resilient means 17 is brought into lnitial radial compression upon assembly of the coupling 10. The resilient means 17 contacts completely in the circumferential direction of the coupling 10 at least a portion of ~aid axially elongated inner surface 18 of the outer member 12 and the axially elongated periphery 26 of the inner member 14.
When viewed in the CrosS section shown in Figure 2, the resilient means 17 contacts all of the periphery 26 of the bushing 15. In this cross-section, the periphery 28 of the resilient means 17 is itself contacted by all of the inner surface 18 of the outer member 12. As shown in Figures 2 and 3, there are no void~ between the oppo~ed .working curfaces 26, 18 of the inner and outer members since this space i~ occupied completely by the resilient means 17. The resilient means 17 is prefenably contlnuous in the circumferential direction of the coupling 10 and bonded to one of the respective inner or outer rotary 35- members 14,12. It is most preferable that the resilient means 17 be bonded to the inner rotary member 14 such as .SU. 169~69 to bushing 15 illustrated in Figures 1 through 5.
The resilient means 17 is formed of an elastic polymeric material and is preferably made of natural rubber, or of a synthetic polyisoprene blended with styrene butadiene rubber. When rubber is used for the resilient means, it should be compounded to a durometer of about 75 to 80 Shore A Hardness and be high in tear strength and adhesion as measured on a peel-type strip test such as ASTM D429, Method B. Compression set should be as low as obtainable while maintain~ng the above given properties and preferably should not exceed 25 to 30%
when measured according to ASTM D395, Method B, for 22 hours at about 158F. It is believed that other elasto-meric materials may be satisfactory in this application, including polyurethane. Specific formulations are not presented herein as suitable formulations are known or readily developed by those skilled in the art.
The undeformed configuration o~ a preferred embodl-ment of the resilient means 17 is shown in Figures 4 and 5 in which the bushing 15 of the coupling 10 qhown in Figures 1, 2 and 3 is illustrated including in its as-manufactured, undeformed state the resilient mean~l7 of vulcanized rubber of thickness T bonded to the central portion 32 of its periphery 26. The thickness T of the resilient means 17 as measured along a radius extending perpendicularly from the axis of rotation 23 of the - bushing 15 is i~ a preferred embodiment reduced about - 35% upon installation of the bushing 15 with the resilient means 17 bonded thereto into the outer member 12. The configuration of, the outer member 12 and the bushing 15 are prefer~bly chosen such that the resilient means 17 is further compressed at maximum torsional load to about 60% of its original undeformed radial dimension.
In oth~r words, ~hen the corner~ 30 of the inner member 14 are nearest the flat areas 20 of the outer member 12, ~ 169669 the resilient means 17 is compressed about 60% in the radial direction at those areas.
Because the resilfent means 17 undergoes considerable radial compression upon assembly of the coupling 10 the resilient elastomeric means in its undeformed, as-manufactured state is preferably of considerably greater radial dimension and lesser axial dimension than in the assembled coupling. In this regard compare Figure 5 with Figure 3. For this reason the resilient means 17 preferably in its undeformed state contacts and is bonded to the central portion 32 of the periphery 26 of the bushing 15 and is of generally unifbrm thickness T
throughout both its circumferential and axial extent in central portion 32. The resilient means 17 preferably has radiused corners 34-which extend about its circum-ference at its axial extremities and fillets 35 at its junction with the periphery 26 of bushing 15 to reduce stresses at these locations. These stresses are particu-larly high during assembly of the coupling 10. The bushing 15 includes an internal bore 16 for mating en-gagement with a drive shaft such as propeller shaft 24 shown in Figures 1, 2 and 3.
Referring now to Figure 6 there is illustrated another embodiment according to the invention of a rotary coupling 37. The periphery 40 of the inner member 38 when viewed from the end or in a cross section taken normal to the - axis of rotation 41 of the inner member 38 is of generally elliptical configuration. It is believed that the ratio of the major axis to minor axis should be in the range 3 of 1.05 to 1.15 to obtain maximum angular displacement of the inner member 38 and outer member 39 relative to each other without seriously damaging the rubber of resilient means 42 when it is subjected to maximum impact torsional loading. This design permits a full 90 angular displac~ment before the resilient means 42 is sub~ected ~ 169~69 to its maximum radial compression whereas in the embodiment illustrated in Figures 1-5 the resilient means 17 is sub-~ected to its maximum radial compression at 45 displace-ment of the inner member 14 relative to the outer member 5 12. In the embodiment illustrated in Figure 6 the outer rotary member 39 includes an axially elongated inner surface 43 which in a section taken perpendicularly to the axis of rotation 41 includes two arcs 44 of greater radius of curvature which are diametrically opposed from one another. These arcs 44 are connected in alternate manner by two arcs 45 of lesser radius of curvature which are also diametrically opposed from one another. The arcs 44 of greater radius of curvature are located closer to the axis of rotation 41 than the arcs 45 of lesser radius of curvature. As with the embodiments already discussed, the periphery 40 of the inner rotary member 38 opposes the inner surface 46 of the outer member 39. The periphery 40 of the inner member 38 is of a configuration generally corresponding and complementary to that of the lnner surface 46 of the outer member 39 but is of lesser radial dimensions such that the periphery 40 of the inner member 38 is spaced radially fr~m the inner surface of the outer member when each is centered on the axis of rotation 41 and no load is imposed on the coupling.
This spacing need not be exactly equal throughout the circumferential direction. The periphery 40 of the inner member 38 may be mathematically specified and the inner surface 46 of the outer member 39 constructed there-from or mathematically specified. When both are mathematic-ly specified as true elipses, the distance betweenthem will not be a true constant at all polnts. This non-uniformity is believed not to adversely affect the coupling and may provide a means for tuning the torsional load versus angular deflection characteristics of the coupling. Resilien~t elastomeric means 42 is dis-posed between the inner and outer members. The resilient ~ 1~95~9 means 42 is in radial compression and contacts completely in a circumferential direction of the coupling the inner working surface 46 of the outer member 39 and the working periphery 40 of the inner member 38. When no load is 5 imposed on the coupling the corresponding arcs 44,47 of lesser radius of curvature of the outer and inner members are generally aligned. When a torsional load is imposed on the coupling these corresponding areas 44,47 of lesser radius of curvature are angularly displaced relative to one another thus increasing the amount of compression of the resilient means 42 adjacent the arcs 49 of lesser radius curvature of the inner rotary member 38. The resilient means 42 is compressed about 35% from its un-deformed configuration upon assembly of the coupling 37, 15 The periphery 48 of the resilient means 42 before being compressed is shown by dashed lines in Figure 6. The resilient member 42 is of approximately even thickness throughout and is approximately evenly compressed through-out upon assembly of the coupling 37.
In Figure 7 there is shown yet another embodiment of a coupling 50 according to the invention. The outer rotary member 51 includes an axially elongated inner surface 52 which in a section taken perpendicularly to the axis of rotation 53 includes three arcs 54 of greater 25 radius of curvature symmetrically disposed about the axis of rotation 53. The arcs 54 of greater radius o~ curvature are connected in alternate manner by an equal number of arcs 55 of lesser radius of curvature which are also symmetrically disposed about the axis of rotation 53.
The arcs 54 of greater radius or curvature are located closer to the axis of rotation 53 than the arcs 55 of lesser radius of curvature. The center of curvature of each of said arcs lies within the outer boundary of the section of the inner surface 52. The arcs 54,55 are connected 35 to one another without any abrupt change of radius or ~ 169869 of radiu~ of curvature. The configuration depicted in Figure 7 may be called tri-oval. As in the other em-bodlment~ ~hown the resilient means 56 is of sub~tan-tially even thickness throughout between the inner surface 52 of outer member 51 and the periphery 57 of inner member 58 and is ~ub~tantially evenly compres ed upon as~embly o~ the coupling 50. The inner and outer f rotary members are of complementary configuration. The arcs 59 of lesser radius of curvature of the inner rotary member 58 are generally aligned with the arcs 55 of les~er radius of curvature of the outer rotary member when no load is impo~ed onto the coupling and are angularly displaced relative to one another upon impo~ition of a torsional load, thus increasing compression oi the resilient means 56.
A coupling according to the present invention can be designed so as to permit permanent angular displacement or, in other words, rotary slip, ratcheting or indexing or the inner and outer members relative to one another.
In the embodiment ~hown in Figures 1-5 if rotary slip at a predetermined torque is desired the radial distance P from the axis of rotation 23 of the rounded corner~ 30 of the inner member 14 mu~t be le~s than the radial di~-tance r of a bisecting radiu~ normal to the flat areaq 20 of the outer member 12. Expres~ed mathematically, P~ r.
Referring to Figure 6, i~ rotary slip at a predetermined torque is desired the radial distance from the axis of ro-tation 41 of the arc 49 of les~er radius of curvature of the inner member 38 mu~t be le3s than the radlal distance of the arc 44 of greater radiu~ of curvature of the outer member 39.
On the other hand, if it is desired to provide limited angular displacement between the inner and outer rotary members of a coupling according to the invention, this too, can be provided by design choice o~ the relative dimensions of the inner and outer rotary members. For g~69 example, in the embodiment shown in Figures 1-5 the radial distance P from the axis of rotation 23 of the rounded corners 30 o~ the inner member 14 would be es-tablished greater than the radial distance r of a bi-secting radius normal to the flat areas 20 of the outermember 12. Expre~sed mathematically, P~ r. When this relationship exists, upon ~u~fic~ent angular or rotary deflection or displacement of the rounded corners 30 of the inner member 14 relative to those of the outer member 12 the rounded corners 30 of the inner member 14 come into contact with the flat areas 20 of the correspondingly configured outer member 12 and prevent any further angular displacement of the members 12 and 14 relative to one another, Because the resilient means is not fluid, lockup will occur at some value of P~ r, provided the torque load does not càuse total failure of the re~ilient means through exce~sive shearing. At displacements below that at which mechanical loc~up occurs the resilient ela8tomeric means 17 cushions any torque loadlng between the inner member 14 and outer member 12, In similar fashion the dimensions of the inner and outer members in the embodi-ment shown in Figures 6 and 7 can be establi~hed such that upon sufficient angular or rotary deflection of the inner and outer members relative to one another the arcs of lesser radius of curvature of the inner rotary member will come into contact or interference with the arcs of greater radius of curvature of the outer rotary member to prevent further angular displacement of the inner and outer rotary members relative to one another.
It is believed that the radial distance between the inner surface of the outer member and the periphery of the inner member should be established such that the resilient means when ~ormed of rubber is compres~ed about 35% upon assembly of the coupling. Because the inner and outer rotary members are of generally corres-ponding and complementary cross-sectional oonfiguration ~169669 _ 13 -the resilient means is approximately compressed uniformly about the circumference of the coupling. In a preferred high t~rque capability embodiment of the coupling similar to that shown in Figu~es 1-5 the radial distance between the inner surface 18 of the outer member 12 and the periphery 26 of the inner member 14 as well as the radial distance p of the corners 30 of the inner member 14 in comparison to the radial distance r of bisectine radlus normal to the flat areas 20 was chosen such that when the inner member 14 and the outer member 12 are angularly displaced relative to one another so that the corners 30 of the inner member 14 are nearest the flat area 20 of - the inner surface 18 of the outer member 12 the resilient means 17 is compre8sed to about 60% of its new undeformed configuration. It is believed that when rubber is used for the resilient means that maximum radial compression should be restricted to about 60%. An exception to this guideline, of course, exists when the member~ of the coupling are dimensioned 9uch that lnterference of the periphery of the inner member and the inner suriace of the outer member will occur upon sufficient angular deflection.
It ha~ already been explained that the coupling can be designed so as to permit angular slip between its 25 inner and outer members or to be of a lock-up or non-slipping type design. The radius of the corners 30 or areas of smaller radius of curvature on the inner member 14 also have an effect on torque characteristics and the life of the coupling 10 and particularly on the llfe of the intermediate resilient means 17. If the corner~ 30 of the inner member 14 are sharper, that is, of a smaller radius of curvature, when all other factors are equal, it is more likely that the resilient means 17 may become cut, torn or ruptured. It is thus preferable that the circumferential arc length 62 of each rounded corner 30 oi the inner member or arc of lesser radius oi curvature be at least equal to the circumferential dimension 63 of each flat area 64 or arc of greater radius of curva-ture of the inner member 14. It i~ most preferable that the circumferential arc length of each rounded corner 30 or arc of lesser radius of curvature of the inner member be at least 150% of the circumferential dimension of each flat area 20 or area of greater radius of curvature of the respective inner member. In the embodiment shown - in Figures 1-5, which is a preferred embodiment, the cir-cumferential arc length of each rounded corner is equal to or greater than the circumferential dimension of the corresponding flat area of the respective inner member 14, outer member 12 or resilient means 17.
In the embodiment illustrated in Figures 1-5, the periphery 26 of the inner member 14, the inner surface 18 of the outer member 12, and the resilient means 17 are each of generally square cross-sectional configuration and include four flat areas connected by rounded corners and are of generally uniform size throughout the axial extent of the confronting surfaces. No taper in the direction of the axis of rotation is required in a coupling according to the invention, although such taper may be employed to ease a~sembly and disassembly of the coupling.
When used in a marine drive, the coupling i~ removed as a unit from the propeller shaft. The coupling itself is not intended to be serviced in the field due to press fitting of the inner member into the outer member with attendant compression of the resilient means.
The configuration of the inner and outer members and the resilient means have been described to be poly-gonal or polyoval. The minimum number of flat area~, i.e., areas of greater radius of curvature is two and this will usually by employed in a lock-up type design having a limited angular deflection between the inner and outer members of the coupling. All el~e belng held ~966 constant, as the number of flat areas on the inner and outer members is increased it becomes easier to cause the inner and outer members to slip rotationally relative to one another. As the number of flat areas on the inner and outer members is increa~ed the angular displacement between the inner and outer members prior to permanent slip or angular displacement of these members relative to one another is lowered as is the maximum torque transmission capability o~ the coupling for a given over-all physical size, similar compounding for the resilientmeans, and same degree of precompression of the resilient means upon assembly of the coupling. It is believed that about eight flat areas on the inner and outer members are a practical maximum number, It is to be noted that the configuration of the inner and outer members does not have to be that of a regular polygon having rounded corners as illustrated but rather can be rectangular ~ith rounded corners or elliptical, tri-oval or polyoval. A
configuration whi¢h is symmetrlcal about the axis of rotation of the coupling however is preferred to avoid radial displacement of the inner or outer members relative to the axis of rotation upon application of a torque load.
In preferred embodiments, the resilient means is formed of wlcanized rubber and is sized so as to be subjected to substantially equal radial compression at all points about its circumference upon assembly of the inner and outer members to form a coupling of the invention. Increasing the amount of radial compression of the resilient means upon assembly of the coupling will increa~e the torsional spring rate and maximum torque capability of the coupling, all else being equal and vice versa. Preferably the resilient means is adhered to the inner member and has a relatively high adhesion, for exàmple, about 50 pounds per inch width as measured by ; 35 cutting the resilient means and allowing the part to g 16~6~9 roll and thereby peeling the resilient means from the inner member.
The resilient means is preferably molded and bonded to the inner member. Transfer or injection molding are preferred over compression molding since the latter is not believed to be as accurate. It is desired that concentricity of the inner and outer members be maintained and therefore an accurate molding process for evenly forming the resilient means about the inner member is desirable.
The term "axially" and related terms as used herein mean in the direction of or parallel to the axis of rotation of the coupling or that of any of its constituent elements such as the inner member, the resilient means, or the outer member as herein described. The term "radially"
and related terms as used herein mean in a plane inter- -secting the axis of rotation and perpendicular to the axis of rotation as defined hereln, The term "circum-ferentially" and related term~ as used herein mean in a directlon around the axls of rotation as defined herein.
The term "arc" and related terms as used herein mean a curved line or any section of a curve and are not to be limited to a constant radius of curva~,ure but are in-tended to include a continuously changing radius of curvature.
The term "polyoval" as used herein refers to a closed two dimensional figure all of whose boundary portions are straight or curved such that the center of radius of curvature of all points of the boundary lie on or within the figure. An example of a polyoval is shown by the periphery of the inner member in Figure 7, which is a tri-oval. A coupling could, of course, be designed with a greater number of arcs of les~er radius of curvature, with about eight such areas believed to be the practical maximum, - ï7-While certain representative embodiments and details have been shown for the purpose of illustrating the ,n-vention it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing ~rom the spirit or scope of the invention.
Claims (11)
1. In a marine propeller drive having a propeller and propeller drive shaft, the improvement of a resilient, indexing, rotary marine drive coupling having an axis of rotation and being for coupling the propeller and the propeller drive shaft of the marine drive, the coupling comprising: (a) an outer rotary member having an axially elongated inner surface which in section taken perpendicularly to said axis includes at least two arcs of greater radius of curvature symmetrically disposed about said axis connected in alternate manner by an equal number of arcs of lesser radius of curvature, said arcs of greater radius of curvature being located closer to said axis than said arcs of lesser radius of curvature, the center of 2 curvature of each of said arcs lying on or within the boundary of the closed figure defined by said inner surface in said section and the arcs being connected to one another without any abrupt change of radius or radius of curvature, (b) an inner rotary member having an axially elongated periphery opposing the inner surface of said outer member, said periphery being of a cross-sectional configuration generally corresponding and complementary to that of the inner surface of said outer member but being of lesser radial dimensions such that the periphery of said inner member is spaced radially from the inner surface of said outer member when each is centered on said axis and no load is imposed on the coupling, and (c) resilient elastomeric means disposed between said outer and inner members, said resilient means being in radial compression and contacting completely in the circumferential direction of said coupling at least a portion of each of said inner surface and said periphery, (d) in which the corresponding arcs of lesser radius of curvature of the inner and outer members are generally aligned when there is no load imposed on the coupling, and (e) in which the radial distance from the axis of the arcs of lesser radius of curvature of the inner member is less than the radial distance from the axis of the arcs of greater radius of curvature of the outer member and thereby provides permanent rotary displacement of the inner member relative to the outer member.
2. A marine propeller drive according to Claim 1 in which the resilient rotary marine drive coupling includes the outer rotary member having the axially elongated inner surface being of polygonal cross section comprising a series of at least three chordally disposed straight lines connected by rounded corners, and the inner rotary member includes the axially elongated periphery being of polygonal cross section generally corresponding and complementary to that of the inner surface of the outer member, the corresponding straight line in cross section of the outer and inner members being generally parallel when there is no load imposed on the coupling.
3. The marine propeller drive of Claim 1 or Claim 2 in which the radial distance between the inner surface of the outer member and the periphery of the inner member is such that the resilient means is compressed about 35% upon assembly of the coupling and is further compressed to about 60% when the inner member and the outer member are angularly displaced relative to one another such that the arcs of lesser radius of curvature of the inner member are nearest the arcs of greater radius of curvature of the inner surface of the outer member.
4. The marine propeller drive of Claim 2 in which the circumferential arc length of each rounded corner is at least equal to the circumferential dimension of each flat area of the respective inner member, outer member or resilient means.
5. The marine propeller drive of Claim 1 in which the resilient means is continuous in the circumferen-tial direction of the coupling and is bonded to one of the inner or outer rotary members.
6. The marine propeller drive of Claim 1 in which the inner member comprises a metallic bushing adapted to be received on and matingly engage the propeller drive shaft, the resilient means is continuous and is bonded to the central portion of the periphery of the bushing and in its undeformed state is of generally uniform thickness in the central portion of the axial extent of the periphery of the bushing and has radiused circumferentially extending corners and fillets at its axial extremities.
7. The marine propeller drive of Claim 1 in which the inner surface of the outer member, the periphery of the inner member, and the resilient means, when viewed in cross section taken perpendicular to said axis, are each of generally square configuration including four flat areas connected by rounded corners and of generally uniform size throughout the axial extent of their confronting surfaces.
8. The marine propeller drive of Claim 1 in which the resilient means is of vulcanized rubber and is approximately equally compressed at all points about its circumference when no load is imposed on the coupling.
9. The marine propeller drive of Claim 1 in which the outer rotary member includes the axially elongated inner surface being of elliptical cross section and the inner rotary member includes the axially elongated periphery being of elliptical cross section.
10. The marine propeller drive of Claim 1 in which the outer rotary member includes the inner surface being of tri-oval cross section and the inner rotary member includes the axially elongated periphery being of tri-oval cross section.
11. In a marine propeller drive having a propeller and propeller drive shaft, a resilient, indexing, rotary marine drive coupling having an axis of rotation and being for coupling the propeller and the propeller drive shaft of the marine drive, the coupling comprising: (a) an outer rotary member having an axially elongated inner surface of generally square cross-sectional configuration comprising a series of four chordally disposed flat areas connected by rounded corners disposed a great radial distance from said axis than the radial distance of bi-secting radius normal to said flat areas, the circumferentially measured arc length of each rounded corner being at least equal to the circumferentially measured dimension of each flat area, (b) an inner rotary member comprising a metallic bushing adapted to be received on and matingly engage a shaft, said inner member having an axially elongated periphery opposing the inner surface of said outer member, said periphery being of generally square cross-sectional configuration generally corresponding and complementary to that of the inner surface of said outer member but being of lesser radial dimensions such that the periphery of said inner member is spaced radially inwardly from the inner surface of said outer member when each is centered on said axis and no load is imposed on the coupling, and (c) resilient elastomeric means of vulcanized rubber disposed between said outer and inner members and bonded to said inner member, said resilient means being approximately equally radially compressed throughout its circumferential and axial extent between said inner surface and said periphery and contacting completely in the circumferential direction of said coupling at least a portion of each of said inner surface and said periphery, the amount of compression being about 35 percent upon assembly of the coupling and about 60 percent when the inner member and outer member are angularly displaced such that the corners of the inner member are nearest the flat areas of the inner surface of the outer member, (d) in which the corresponding flat areas of the outer and inner members are generally parallel and symmetrically disposed about said axis when there is no load imposed on the coupling, and (e) in which the radial distance from the axis of the rounded corners of the inner member is less than the radial distance of the bi-secting radius of the outer member and thereby provides permanent rotary displacement of the inner member relative to the outer member.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US18152580A | 1980-08-26 | 1980-08-26 | |
| US181,525 | 1980-08-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1169669A true CA1169669A (en) | 1984-06-26 |
Family
ID=22664653
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000383153A Expired CA1169669A (en) | 1980-08-26 | 1981-08-04 | Resilient rotary coupling |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1169669A (en) |
-
1981
- 1981-08-04 CA CA000383153A patent/CA1169669A/en not_active Expired
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