FLEXIBLE COUPLING

Abstract: The flexible coupling includes outer member (14) and inner member (18) drivingly connected in a rotational sense through opposed pairs of flats (20, 24) separated by laminated elastomer-inelastic material (30) bonded to the flats. Four inner flats (24) are squarely arranged and are cylindrincally curved along their lengths about orthogonal axes of curvature (28, 29) intersecting at the axis of rotation of the inner member (26), and are flat across their widths. Four opposed outer flats (20), parallel to the inner flats (24), are flat across their lengths and widths and extend alongside the axis of rotation of the outer member (22). Inner layers (32) of laminated material extend parallel to the inner flats and the outer layers (34) of laminated material, bonded to the inner layers, extend parallel to the outer flats.

Description: FLEXIBLE COUPLING TECHNICAL FIELD This invention is in the field of flexible drive couplings, and more specifically constant velo¬ city universal joint drive couplings for transmitting torque between driving and driven rotary elements. BACKGROUND OF PRIOR ART Prior art flexible drive couplings use sliding and rolling surfaces between relatively moveable parts of the coupling elements. Load capacities and rotational speeds of such couplings are limited, and lubrication requirements critical, particularly in applications designed to accommodate misalignment of more than a fraction of a degree between the driving and the driven components. Constant velocity univer¬ sal joint couplings tend to be complex and costly mechanical elements, requiring rather superprecision manufacturing tolerances and complicated assembly procedures. So-called elastomeric flexible couplings trans¬ mitting torque through a laminated elastomeric-inelas- tic material, either in compression or shear, or a combination of the two are particularly limited in both torque and misalignment capacity. The prior art is also known to use elastomeric materials in univer¬ sal joints in lieu of sliding and rolling bearings at the surfaces transmitting the torque loads. The present invention is intended to overcome various problems associated with flexible drive IjUREAfT O PI couplingsin a unique manner which enables the attain¬ ment of a simple, rugged, non-lubricated constant velo¬ city flexible drive coupling capable of transmitting high loads at high rotational speeds while accommoda¬ ting extreme misalignment between the driving and driven coupling members. SUMMARY OF THE INVENTION The present invention is a unique constant velo¬ city universal joint flexible coupling utilizing basically a foursided square drive between coaxial driving and driven members, with curved and flat laminated elastomeric-inelastic material disposed between the driving surfaces, called "flats", of the coupling, so that no surface sliding or rolling occurs when the driving and driven parts of the coupling move relative to each other. The surfaces of the flats, of the inner coupling member are cylindrically longitudinally curved about orthogonal axes of curvature intersecting at the longitudinal center line of the member, but are planar across their widths. The cooperating flats, of the outer member of the coupling extend parallel to the rotary axis of the outer member of the coupling, and are not curved at all. A laminated elastomeric-inelas¬ tic material is interposed between and bonded to the opposing flats of the inner and outer members of the coupling. The inner layers of laminated material extend parallel to the flats of the inner members; the outer layers of the laminated material extend parallel to the flats of the outer member. All the layers of laminated material are bonded to themselves and to the flats. Torque loads about the axis of the coupling are transmitted through the flats and through the laminated material in a compressional sense. The nature of the laminated material is such that it is virtually incom¬ pressible transversely of the laminations, while it is relatively soft in resisting shear or torsion loads acting parallel to the planes of the laminated layers. Therefore, relative longitudinal movement or axial misalignment between the inner and outer coupling « members is accommodated imply by the deformation of the laminated material in shear or torsion senses, with the specific layers undergoing elastic deforma¬ tion and the nature and degree of such deformation depending upon the instantaneous azimuthal location of the particular flats between which the laminate is situated during rotation of the coupling. Axial displacement between inner and outer coupling members is accommodated by the elastic deformation of the outer layers of laminated material between opposed flats. However, a rigid trunion joint is contemplated for use between inner and outer members to prevent relative axial displace¬ ment between the coupling members, while still leaving undisturbed all of the other ' characteristics of the basic coupling embodying the invention. The trunion joint is also provided with a laminated bearing arrangement so that this embodiment, like the basic embodiment, does not require sliding or rolling surfaces to accommodate relative motion between driving and driven parts. BRIEF DESCRIPTION OF THE DRAWINGS With reference to the drawings forming a part of the specification, FIGURE 1 is a vertical sectional view of a flex- ible coupling embodying the present invention; FIGURE 2 is a cross sectional view taken along line II-II of FIGURE 1; FIGURE 3 shows the coupling of FIGURE 1 with the elements misaligned; FIGURE 4 shows the coupling of FIGURE 1 with the elements axially displaced relative to each other; FIGURE 5 shows an alternate embodiment of the coupling embodying this invention, this embodiment in¬ corporating a trunion assembly; FIGURE 6 is a view taken along line VI-VI of FIGURE 5; FIGURE 7 shows a coupling of FIGURE 5 axially mis¬ aligned and FIGURE 8 shows a coupling used in pairs to trans¬ mit drive torque through offset, parallel shafts. DETAILED DESCRIPTION With reference to FIGURE I, the flexible coupling embodying the present invention includes, for example, a first and second shaft 10 and 12, either of which may be driven by the other. The first shaft 10 includes an outer member 14 provided with an internal cavity 16 in which is disposed an inner member 18, all as illustrated in FIGURES 1 and 2. The internal cavity 16 within outer member 14 is provided with flat wall portions 20 which define four outer flats that are symmetrically disposed about and face the longitudinal axis 22 of outer member 14. The inner member 18 is disposed centrally within the cavity 16 and includes four external surfaces sym¬ metrically located about the longitudinal axis 26 of shaft 12 and inner member 18. The four surfaces 24 de¬ fine inner flats that face the four outer flats defined by the flat wall portions 20 of outer member 14. The in¬ ner flats 24, as seen in FIGURES 1 and 2, are cylindrical- ly curved along their lengths (along the longitudinal axis 26) about orthogonal axes of curvature 28,29, but they are substantially planar across their widths in a circumferential sense about longitudinal axis 26, as best seen, in FIGURE 2. The inner flats 24 are located equidistant from and face the outer flats 20 as shown in FIGURE 2 to define spaces between opposed pairs of inner and outer flats. A bonded assembly of elastomer-inelastic layers 30 is disposed between and connected by bonding to each pair of opposed inner and outer flats 24-40. The bonded as¬ sembly extends over at least substantially the full width of the inner flats 24, as shown in FIGURE 2, and the as¬ sembly 30 includes a plurality of inner layers 32 adja¬ cent and extending parallel to the inner flats 24, and a plurality of outer layers 34 adjacent and extending par¬ allel to the outer flats. An intermediate layer 36 has dissimilar curved surfaces on its inner and outer sides, including an inner surface 38 extending parallel to inner flat 24 and an outer surface 40 extending parallel to outer flat 20. The bonded assembly 30 comprises, for example, alternate layers of elastomer and metal, or other inelastic material. The intermediate layer 36 may be either elastic or inelastic material. The charac¬ teristic of such a laminated assembly is well known; namely, it is rigid in compression (virtually incompres¬ sible) while it is relatively soft in shear, that is in a direction parallel to the layers. Thus, with reference now particularly to FIGURES 2 through 4, the laminated assembly 30 transmits rotational driving forces about axes 22,26 transmitted through the flats 20-24 and through the bonded assembly 30 acting directly in compression. It will be observed that there is virtually no lost motion between driving and driven elements, large forces can be transmitted through the flats; and there are no sliding or relatively rotating surfaces. The torque transmission is direct between the members. As seen in FIGURE 3, misalignment of the axes 22,26 is accomodated by the elastic deformation of the elastomeric layers of the inner layers 32 of the bonded assembly 30. Due to the cylindrical curvature of the inner flats 24 along the longitudinal axis 26, the upper and lower assemblies 30 shown in FIGURE 3 will deform as O ! ^ illustrated, while the other two flat planar laminated assemblies not shown (those to the left and right in FIGURE 2) will torsionally deform about the axis 28. Axes 28 and 29 intersect at axis 26. As seen in FIGURE 4, relative axial displacement of members 10, 12 is accomodated by the elastic deforma¬ tion of the elastomeric layers in the outer layers 34 of bonded assembly 30. It will readily be appreciated that a combination of angular misalignment such as shown in FIGURE 3 and relative axial displacement between the members as shown in FIGURE 4 will be accomodated by the elastic deformation of the elastomeric layers comprising the inner and outer layers 32, 34, respectively, of the bonded assembly 30. Rotatable members 10 and 12 are illustrated for exemplary purposes as drive shaft elements. However, it should be understood that the concept of the present in¬ vention is applicable to any arrangement of driving and driven elements. For example, the outer member could be a gear wheel or a fly wheel with the appropriate inter¬ nal cavity 16 being provided within the respective member. Also, the number of layers in the bonded assembly 30 could be varied to suit particular operating requirements. Obviously, more laminationswould permit a greater degree of misalignment between the driving and driven elements, as well as permit a greater degree of relative axial dis¬ placement between these members. Also, if it is desired to obtain a greater degree of freedom in terms of angular misalignment, a greater number of inner layers 32 can be provided as compared to the number of outer layers 34. Conversely, a greater or lesser number of outer layers 34 can be utilized to accomodate a greater or lesser de¬ gree of relative axial displacement between the rotary members. An alternate embodiment of the present invention is shown in FIGURES 5, 6 and 7. In accordance with this embodiment, relative axial displacement between members 10 and 12 is prevented by using a trunion pivot assembly which will now be described. With reference to FIGURES 5 and 6, the outer mem¬ ber 14 is provided with apertures 46 which extend through each of the outer flats 20. The center line of each of the apertures 46 lies along the respective one of said orthogonal axes 28, 29 that extends through the outer flat 20 through which the aperture normally extends when axes 22 and 26 are aligned. Two opposed pairs of trunion pivots 48 extend through the apertures 46, the inner ends of the trunion pivots 48 being connected to one of the inelastic layers 50 among the intermediate layer 36 shown in FIGURES 1 and 2, with said intermediate layer 36 and said layer 50 being considered as an outer layer in the context of the present specification. That is to say, the inner ends of trunion pivots 48 can be connected to any of the non-elastic layers forming a part of the outer layers 34 of the bonded assembly, including the inter¬ mediate layers 36 or 50. The intermediate layers 36 or 50, because of their geometry and location, actually perform functions of both the inner and outer layers of the bonded assembly. Nevertheless, it should be under¬ stood that when the trunion pivot means is described as being rigidly connected to at least one of the inelastic outer layers of the bonded assembly 30, such layer may include the intermediate layer 36 or 50 or any of the rigid layers of outer layers 34. Between the outer periphery of the trunion pivots 48 and the inner surfaces of the apertures 46, there is provided another bonded assembly of laminated elastic- inelastic material 52 which in each instance is bonded on its either side to the periphery of the pivots 48 and the inner sidewall surface of the apertures 46. As illustrated in FIGURE 7, angular misalignment between longitudinal axes 22 and 26 of members 10 and 12, respectively, is accomodated by elastic deformation of layers 32 and the torsional elastic deformation of the layers 34. The trunion pivots 48 will prevent relative axial displacement between the members 10 and 12, with the pivots 48 rotating within apertures 46 and the elas¬ tomeric layers of the laminated assembly 50 undergoing torsional elastic deformation to accommodatethe relative pivotal motion between trunion pivots 48 and the side- walls of the apertures 46. The trunion pivots 48 resist forces tending to axially displace members 10 and 12 relative to each other by reacting the loads through the laminate assembly 30 in compression. FIGURE 8 exemplifies a specific application of the flexible coupling of this invention. In this example, shafts 54, 56 are offset from each other and connected through an intermediate connecting shaft 58. Shaft 58 includes outer members 60 at either end that correspond with outer member 14 in FIGURE 1. Internal members 62, 64 are provided with the internal flats of the present invention, while the outer members 60 are provided with internal cavities that include planar sidewall portions carrying the outer flats described previously in con¬ nection with FIGURES 1-7. It will be apparent that laminated members 66, 68 which correspond to laminate assembly 30 previously described will permit the trans¬ mission of torque between the shafts 54 and 56 due to the ability of the flexible coupling of the present in¬ vention to accomodate the misalignment and relative axial displacement between the rotating members that may occur. The embodiments described- in this specification and illustrated in the drawings are considered to be exemplary only, and depict a presently preferred mode - REA OΓΛPI ' ^R AT of carrying out the present invention. Such examples are not intended to limit the scope of the invention in any way, such invention being that which is defined in the claims set forth below.

Claims: WHAT IS CLAIMED IS; 1. A flexible coupling comprising an outer member rotatable about a first longi¬ tudinal axis and having an internal cavity with flat wall portions defining four outer flats symmetrically disposed about and facing towards the first longitudinal axis; an inner member disposed at least in part centrally within the said cavity and having external surfaces symmetrically located about a second longitudi¬ nal axis, said surfaces defining four inner flats, said inner flats being cylindrically curved along their lengths along the second longitudinal axis about ortho¬ gonal axes of curvature that intersect at the second axis, said orthogonal axes lying in a common plane ex¬ tending normal to the second axis, and being flat across their respective widths in a circumferential sense about the second axis, said inner member being rotatable about the second axis, and said inner flats being oppositely spaced equidistant from and facing said outer flats to define spaces between opposed pairs of inner and outer flats; a bonded assembly of elastomer-inelastic layers disposed between and connected by bonding to each pair of opposed inner and outer flats and extend¬ ing over at least substantially the full width of the inner flats, said bonded assembly including a plurality of inner layers adjacent and extending parallel to the inner flats, and a plurality of outer layers adjacent and extending parallel to the outer flats. 2. The coupling according to Claim 1, wherein the portion of the inner member that includes the inner flats is substantially square in transverse cross sec¬ tion. 3. The coupling according to Claim 2, wherein the said cavity flat wall portions define substantially a square cavity. 4. The coupling according to Claim 1, wherein said first and second longitudinal axes are normally coextensive, and said inner and outer members are sec¬ tions of drive shafts extending along said axes. 5. The coupling according to Claim 1, wherein one of said outer layers in each bonded assembly has dissimi¬ lar curved surfaces, including an inner surface extend¬ ing parallel to the respective inner flat and an outer surface extending parallel to the respective outer flat. 6. The coupling according to Claim 5, including apertures in each of the outer flats, the center line of each aperture extending along the respective one of said orthogonal axes projected through the outer flat in which the aperture is provided when said first and sec-., ond longitudinal axes are aligned; and trunion pivot means centrally supported with¬ in each of the apertures, each trunion pivot means being rigidly connected to at least one of the inelastic outer layers of said bonded assembly of elastomer-inelastic layers adjacent the respective apertures. 7. The coupling according to Claim 6, wherein each trunion pivot means is rigidly connected to said layer having dissimilar curved surfaces, said layer having, dissimilar curved surfaces being an inelastic layer in said bonded assembly. " ϋREAcT 8. The coupling according to Claim 6, wherein the apertures have inner surface areas; said trunion pivot means are pin members that are each centrally disposed within a respective aperture, each pin member being smaller in cross sectional area than the cross sectional area of the aperture to thereby leave a space between the pin member and the inner surface area of its respec¬ tive aperture; and a bonded assembly of laminated elas¬ tomer-inelastic material disposed between each pin and the inner surface of the respective aperture in which the pin is located, each of the last said bonded assem¬ blies being also bonded to the pin and the inner surface area of the aperture, the layers of each of the last said bonded assemblies being cylindrically curved about the center of each respective aperture.

Inventors: GREENE J
Applicants: GREENE J
Application year: 1978
Main classification: F16D3
IPC codes: B32B3, F16D3