GB2060135A

GB2060135A - Shaft Coupling

Info

Publication number: GB2060135A
Application number: GB8031260A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-10-09
Filing date: 1980-09-26
Publication date: 1981-04-29
Also published as: IT8049841A0; FR2467321A1; AU530185B2; DE3038072A1; CH649353A5; IT1128587B; DE3038072C2; GB2060135B; AU6287980A; CA1151885A; FR2467321B1

Abstract

A coupling for transmitting torque between two shafts comprises two annular members (16, 18) for connection to the two shafts (12, 14) and an intermediate member (20) also of annular form connecting the two annular members (16, 18), the intermediate member (20) having two pairs of generally parallel arm portions (36, 52), each associated with one of the two annular members (16 or 18), each arm portion (36, 52) being connected by its free end (40, 56) to an axially extending connecting element (44, 60) on the associated annular member (16 or 18). <IMAGE>

Description

SPECIFICATION Coupling This invention relates to couplings and more particularly to couplings of the type adapted to transmit torque between two shafts.

The art of coupling two shafts together so that the torque of one is transmitted to the other is an old and highly developed art. Perhaps the simplest coupling consists essentially of a sleeve which is capable of receiving within its opposite ends the free end portions of the two shafts to be connected. Such a simple coupling will function quite well provided that the two shafts are exactly in line. Where misalignment occurs, either wanted or unwanted, the coupling must be constructed so as to accommodate such misalignment. A major characteristic of any coupling which is used to accommodate misalignment is that the coupling should be capable of transmitting the torque from one coupling to the other so that the torque output exactly conforms at all times with the torque input.For example, it is well known that a conventional universal joint, while capable of accommodating angular misalignment, has the characteristic of converting a uniformly applied input torque to a cyclically imposed or sinusoidal output torque. Considerable complexity is required to be introduced into the coupling in order to insure the uniform transmission of torque.

A universal joint is a coupling which is designed primarily to transmit torque between two shafts which are angularly related to one another. Angular displacement constitutes one of three possible misalignments which can occur between two shafts. A second important misalignment is a displacement of the two shafts so that the axis of rotation of one is displaced parallel to the other axis. A coupling capable of accommodating parallel misalignment while maintaining uniform torque transmission is disclosed in my U.S. patent No. 3,242,694, dated March 29, 1 966. The three disc, six link coupling disclosed in this patent has been and is now produced commercially under the Trademark "SCHMIDT COUPLINGS". The third misalignment capability is misalignment in the axial direction which, when presented by itself, can be readily accommodated.

When substantial single misalignments are contemplated it is preferable to utilize a coupling designed specifically to accommodate that single misalignment. However, a much more frequently presented situation in torque transmission is the need to join two shafts which are designed to be in alignment but which may in actual practice present any one or more than one of the abovedescribed misalignments to a small extent. A single coupling designed to accommodate any one or a combination of all three of the aforesaid misalignments is disclosed in my prior U.S. patent 3,791,170. The coupling disclosed in this patent is similar to the original SCHMIDT coupling in its basic constructionfin that it is made up of three discs interconnected by links through pin connections.In order to provide for all three types of misalignment it is necessary to provide spherical bearings in at least some of the pin connections.

As indicated in my patent No. 3,791,170, a significant advantage of the arrangement provided is that like the SCHMIDT coupling it is capable of transmitting the torque uniformly from the driving shaft to the driven shaft. The coupling disclosed in my patent 3,792,270, is commercially marketed under the name "SCHMIDT In-Line Coupling". While the SCHMIDT In-Line Coupling does a highly acceptable job in uniformly transmitting torque between two shafts which may have misalignment, as aforesaid, the cost involved in securing the precision required is such as to discourage widespread use. Thus, unless in a particular application precision is sufficiently important to warrant the costs involved, less expensive couplings are utilized. Usually these less expensive couplings embody resilient elements which are either compressed, stretched or flexed during operation.Examples of couplings which utilize flexible elements are contained in the following U.S. patents: 1,390,514; 2,181,888; 2,566,575; 2,721,457; 2,864,245; 2,867,102; 2,867,103; 2,907,563; 3,625,024; 4,019,345; and 4,033,144. (See also Lovejoy Saga-7 Coupling).

While the above list cannot be considered exhaustive of the many thousands of couplings described in the patented literature, they serve to exemplify the difficulty encountered in undertaking to provide a coupling which has both the basic capability of transmitting torque uniformly and the capacity to readily accommodate any one or any combination of the aforesaid three misalignments. While all of the above-noted patents utilize flexible or resilient elements which tend to reduce costs, not one of these prior art couplings provides the dual capability of transmitting torque uniformly and accommodating any one or any combination of the aforesaid three misalignments.

Accordingly, the present invention seeks to provide a coupling of simplified construction which utilizes material resilience and flexibility (i.e. material displacement) to accommodate misalignments and which also has the capability of transmitting the torque from the input shaft to the output shaft uniformly.

According to the invention, there is provided a coupling for transmitting torque between two shafts comprising two annular members, each for connection to one of the shafts and an intermediate member also of annular form connecting the two annular members, the intermediate member having two parts of generally parallel arm portions and each annular member having a pair of axially extending connecting elements each connected to the free end of one arm portion of an associated pair of the arm portions.

Further according to the invention, there is provided a coupling for transmitting torque from a first torque from a first shaft to a second shaft while accommodating parallel, angular and/or axial misalignment between the axes of said first and second shafts, said coupling comprising: a first annular member having means for fixedly securing the same to the first shaft for rotation therewith about an axis of rotation coincident with the axis of the first shaft, a second annular member having means for fixedly securing the same to the second shaft for rotation therewith about an axis of rotation coincident with the axis of the second shaft, a third intermediate member having an axis of rotation aligned with the axes of rotation of said first and second annular members when the axes of the latter are aligned.

said intermediate member including an annular portion disposed between said first and second annular members and first and second pairs of elongated generally parallel arm portions operatively associated with said first and second annular members respectively, each of said arm portions including a fixed end fixedly inter connected with said annular portion within the axial extent thereof and a free end, A first pair of connecting elements fixedly projecting axially from said first annular member and connected with the free ends of said first pair of parallel arm portions at positions related to the longitudinal extent of said first pair of parallel arm portions and the position of fixed connection of the fixed ends thereof with said annular portion so as to cause torque fixedly transmitted to said first annular member by the first shaft to be transmitted longitudinally through one of said first pair of arm portions to said annular portion under tension and through the other of said first pair of arm portions to said annular portion under compression while enabling through transverse material flexure of said first pair of arm portions the-following relative motions of said annular portion with respect to said first annular member, (1) an angular movement about an axis extending generally in said first transverse direction, and (2) an axial movement, and a second pair of connecting elements projecting axially from said second annular member and connected with the free ends of said second pair of parallel arm portions at positions related to the longitudinal extent of said second pair of parallel arm portions and the position of fixed connection of the fixed ends thereof with said annular portion so as to cause torque transmitted to said annular portion to be transmitted lingitudinally through one of said second pair of arm portions to said second annular member under tension and through the other of said second pair of arm portions to said second annular member under compression while enabling through transverse material flexure of said second pair of arm portions the following relative motions of said annular portion with respect to said second annular member: (1) an angular movement about an axis extending generally in said second transverse direction, and (2) an axial movement.

In the embodiments where the coupling is capable of accommodating not only angular and axial movement but parallel movement as well, parallel motion is accommodated through transverse material flexure of the first pair of parallel arm portions in a parallel linkage type substantially rectilinear movement in a first transverse direction generally perpendicular to the longitudinal extent of the first pair of parallel arm portions and through a transverse material flexure of the second pair of parallel arm portions in a parallel linkage type substantially rectilinear movement in a second transverse direction generally perpendicular to the longitudinal extent of the second pair of parallel arm portions and the first transverse direction.In the embodiments where the coupling is torque rigid, torque is transmitted longitudinally through each pair of parallel arm portions under both tension and compression without longitudinal material displacement whereas in the torque flexible coupling embodiment longitudinal material displacement is allowed to take place through flexure.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which: Figure 1 is a side elevational view of one form of a coupling embodying the principles of the present invention; Figure 2 is an end view taken along the line 2-2 of Figure 1; Figure 3 is a face view of an intermediate member of the coupling; Figure 4 is a sectional view taken along the line 11 of Figure 2; Figure 5 is an exploded side elevational view 15 of the coupling; Figure 6 is a fragmentary section view similar to Figure 4 of a coupling of modified form; Figure 7 is a fragmentary vertical sectional view of a first coupling member of modified form; Figure 8 is a side elevational view of another form of coupling embodying the principles of the present invention; Figure 9 is an end view taken along the line 9-9 of Figure 8; ; Figure 10 is a face view of an intermediate member of the coupling of Figure 8; Figure 11 is a sectional view taken along the line 11-11 of Figure 9; Figure 12 is an exploded side elevational view of the coupling of Figure 8; Figure 1 3 is a fragmentary sectional view similar to Figure 11 of a coupling of another modified form; Figure 14 is a fragmentary vertical sectional view of a first coupling member of modified form; Figure 1 5 is a side elevational view of still another form of coupling embodying the principles of the present invention; Figure 16 is an end view taken along the line 16-16 of Figure 15; Figure 1 7 is a face view of an intermediate member of the coupling shown in Figures 1 5 and 16;; Figure 1 8 is a side elevational view of stili another form of a coupling embodying the principles of the present invention; Figure 1 9 is an end view taken along the line 19-19 of Figure 18; Figure 20 is a face view of an intermediate member of the coupling of Figure 18; Figure 21 is a sectional view taken along the line 21-21 of Figure 19; Figure 22 is an exploded side elevational view of the coupling of Figure 18; Figure 23 is a fragmentary sectional view similar to Figure 21 of a coupling of modified form; Figure 24 is a fragmentary vertical sectional view of a first coupling member of modified form; Figure 25 is a view similar to Figure 20 of an intermediate member of modified form; and Figure 26 is a side elevational view of the intermediate member shown in Figure 25.

Referring now more particularly to the Figures 1 to 5 of the drawings, there is shown therein a coupling, generally indicated at 10, embodying the principles of the present invention, which has the capability of uniformly transmitting torque from a first shaft, indicated in phantom lines at 12 in Figure 1, to a second shaft, indicated at 14 in phantom lines in Figure 1, while accommodating parallel, angular and/or axial misalignment between the axes of the first and second shafts.

The coupling consists essentially of three members which include first and second annular members, generally indicated at 1 6 and 18, suitably fixed to the first and second shafts 1 2 and 14 respectively, and an intermediate member, generally indicated at 20, disposed between the first and second annular members 1 6 and 1 8 and operatively connected therewith in a manner hereinafter to be more fully described.

The first and second annular members 1 6 and 1 8 are preferably of substantially identical construction so that a description of one will suffice to give an understanding of both.

Preferably, each of the annular members is of constant cross-sectional configuration throughout its axial extent so that each is susceptible to being initially fabricated by an extrusion process. Under these circumstances, a preferred extrusion material is aluminum or suitable alloys thereof particularly adapted for extrusion processing. It will be understood however, that while an extrudable configuration is preferred, each of the members may be machined, molded or otherwise fabricated by any other appropriate material such as ferrous metals, resinous plastics or the like.

As best shown in Figure 2, each of the annular members 1 6 and 1 8 is constructed so as to include a ring-shaped annular portion 22 having a pair of connecting element receiving portions 24 extending radially outwardly therefrom at positions spaced apart approximately 1 200C. In order to render each annular member symmetrical about its axis of rotation, a third portion 26 similar in configuration to the pair of portions 24 extends radially outwardly from the ringshaped annular portion 22 at a position spaced apart 1200 from each of the other two portions 24.In addition, each member 16 and 1 8 also includes three set screw receiving portions 28 which extend radially outwardly from the annular portion 22 to an extent considerably less than the portions 24 and 26 at positions spaced equally between the portions 24 and 26.

In the embodiment shown in the drawings, three set screws 30 are mounted so as to extend radially through the portions 28 and the adjacent sections of the annular portion 22. It will be understood that only one set screw may be provided and that such set screw may be utilized to rigidly secure a key member within a keyway formed in the interior periphery of the annular portion. Also it will be understood that any other known manner of effecting the fixed connection between each of the annular members and the associated shaft may be utilized if desired. It will be noted, however, that each mounting is such that the symmetrical axis of the respective member is coincident with the axis of the shaft to which it is fixed.

The intermediate member 20 is preferably molded of a plastic material, a preferred material being polyoxymethylene resin, examples of which are available commercially under the trademarks CELCONt) and DELRIN(H). While these materials are preferred and are regarded to be quite satisfactory in operation, it will be understood that other material having the required characteristics hereinafter set forth may be utilized if desired. In the embodiments shown, the intermediate member constitutes a single molding of the aforesaid polyoxymethylene resinous material.As shown, the intermediate member includes a ring-shaped annular portion 32 having a cylindrical interior periphery 34 of a diameter size greater than the diameter size of the central shaft openings in the annular members 1 6 and 18 so as to permit the shaft 12 and/or the shaft 14 to extend axially into the axial space occupied by the intermediate member without contacting the same while accommodating the aforesaid parallel, angular and/or axial misalignment. The intermediate member 20 also includes a first pair of generally parallel arm portions 36 which are associated with the first annular member 16. Each of the arm portions 36 includes a fixed end 38 which is fixedly connected with the annular portions 32 within the axial extent thereof as by an integral connection.Each arm portion 36 also includes a free end 40 having a cylindrical opening 42 extending therethrough in a direction perpendicular to the axis of the intermediate member 20. Each of the free ends 40 is of generally cylindrical shape having an axial extent which is coextensive with the associate arm portion 36 and annular portion 32 and projects therebeyond in a direction toward the first annular member a short distance as, for example, approximately 1/3 to 1/2 the axial extent of the arm portion and annular portion 32.

The pair of free ends 40 is connected to the first pair of projecting portions 24 of the first annular member 16 by a pair of shoulder bolts 44.

As best shown in Figures 4 and 5, shoulder bolts 44 are of generally conventional construction and include central cylindrical sections 46 having threaded sections 48 extending from one end thereof and an enlarged head 50 formed on the other end. The cylindrical sections rotatably engage in axially coextensive relation within the cylindrical openings 42 while the threaded sections 48 threadedly engaged within threaded openings 51 extending axially through the connecting element receiving portions 24 of the first annular member 16.

It will be noted that the operative connection between the first annular member 1 6 and intermediate member 20 provided by the connecting elements 44 is related to the longitudinal extent of the pair of parallel arm portions 36 and the position of fixed connection of the fixed ends 38 thereof with annular portion 32 such as to cause torque fixedly transmitted to the first annular member 1 6 by the first shaft 12 to be transmitted longitudinally through one of the portions 36 to the annular portion 32 under tension and through the other arm portion 36 under compression. With reference to Figure 2, when annular member 1 6 is rotated clockwise, the arm portion 36 in the upper right-hand quadrant of the Figure is in compression while the other arm portion 36 in the lower left-hand quadrant is in tension.Reversing the direction of rotation of the annular member will reverse the arm portion in compression and tension.

It will be noted that when the axes of the first and second annular members are in alignment the annular member 20 has an axis which is coincident therewith. The annular portion 32 has its axis coincident with this axis and the parallel arm portions 36 have their longitudinal extent so positioned that forces transmitted longitudinal therethrough act essentially tangentially to the axis of the intermediate member. It will also be noted that the transverse extent of each arm portion 36 measured in the axial direction is substantially less than the longitudinal extent of the arm portion and substantially greater than the transverse extent of the arm portion measured in the radial direction.Consequently, since torque transmittal from the first annular member to the intermediate member is along a line generally coincidental with the longitudinal extent of the arm portions 36 substantially no material displacement occurs by virtue of the torque transmission and hence the torque which is imparted to the first annular member 16 will likewise be uniformly transmitted to the annular portion 32 of the intermediate member. While the arm portions 36 remain rigid in the direction of torque transmission and therefore accomplish uniform torque transmission, they are capable of flexing transversely. With the arrangement shown transverse flexing in a radial direction is accommodated more readily than transverse deflection in an axial direction due to the relative material thickness previously noted.

By virtue of the connection of the free ends 40 and fixed ends 38 of the arm portions 36, transverse deflection in a radial direction of the arm portions results in parallel linkage type of translational movement in a transverse direction which extends in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 36. In this regard it will be noted that a plane passing through the axis of the intermediate member which is perpendicular to the longitudinal extent of the parallel arm portions 36 bisects the arm portions so that the amount of material in each arm portion on one side of the plane is generally equal to the amount of material on the opposite side thereof.The parallel linkage type translational movement is accomplished by a pivotal movement of the free ends 40 of the arm portions 36 by virtue of the rotatable movement of the cylindrical sections 46 of the connecting elements 44 within the cylindrical openings 42 of the free ends 40 and a flexure or material displacement of the arm portions 36 about the fixed ends 38 thereof. The pivotal connection of the connecting elements 44 with the free ends enables each arm portion to act in the nature of a diving board or spring board. An arrangement of this type permits a greater degree of flexure.In situations where a lesser degree of parallel misalignment is to be accommodated the connection between the free ends of the arm portions and the connecting element can be a fixed connection, as for example, by extending a fastener radially through each fixed end and the associated connecting element.

The transverse flexure of the arm portions 36 in the axial direction accommodates an angular displacement of the axis of intermediate member 20 with respect to the axis of the first annular member 1 6 about an axis which extends in a direction perpendicular to the longitudinal extent of the arm portions 36. Transverse flexure of the arm portions 36 in the axial direction also accommodates axial displacement as well. Both the angular and axial displacement can take place in both directions without interference by virtue of the axial projections of the free ends 40 of the intermediate member 20. In this regard it will be noted that each of these projections may be provided by a separate washer or as part of the associated connecting element in which case the intermediate member is rendered susceptible to fabrication by extrusion techniques.

The intermediate member 20 also includes a second pair of generally parallel arm portions 52 disposed so that their longitudinal extent is in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 36. Each arm portion 52 is constructed in a manner similar to the arm portions 36 to include an integral fixed end 54 and a free end 56 having a cylindrical opening 58 extending therethrough to receive a connecting element 60. Each of the connecting elements 60 is of similar construction to the connecting elements 44 consisting essentially of a shoulder bolt having a cylindrical central section 62 with a threaded section 64 of reduced diameter on one end thereof and a head 66 on the other end thereof.The cylindrical sections 62 of the bolts 60 rotatably engage in axially coextensive relation within the cylindrical openings 58 while the threaded sections 64 threadedly engage within threaded openings extending axially through the connecting element receiving portions 24 of the second annular member 18.

It will be noted that the operative connection between the second annular member 18 and intermediate member 20 provided by the connecting elements 44 is related to the longitudinal extent of the pair of parallel arm portions 52 and the position of fixed connection of the fixed ends 54 thereof with annular portion 32 such as to cause torque transmitted to the annular portion through arm portions 38 to be transmitted longitudinally through one of the arm portions 52 to the second annular member 1 8 under tension and through the other arm portion 52 under compression. With reference to Figure 2, when the annular portion 32 of the intermediate member 20 is rotated clockwise, the arm portion 52 in the upper left-hand quadrant of the Figure is in tension while the other arm portion 52 in the lower right-hand quadrant is in compression.As before, reversing the direction of rotation of the intermediate member 20 will reverse the arm portions in compression and tension.

Again it will be noted that forces transmitted longitudinally through the arm portions 52 act essentially tangentially to the axis of the intermediate member 20. It will also be noted that the transverse extent of each arm portion 52 measured in the axial direction is substantially less than the longitudinal extent of the arm portion and substantially greater than the transverse extent of the arm portion measured in the radial direction. Consequently, since torque transmittal from the annular portion 32 to the second annular member is along a line generally coincidental with the longitudinal extent of the arm portions 52 substantially no material displacement occurs by virtue of this torque transmission and hence the torque which is imparted to the annular portion 32 of the intermediate member will likewise be uniformly transmitted to the second annular member 18.

While the arm portions 52 remain rigid in the direction of torque transmission and therefore accomplish uniform torque transmission, they are capable of flexing transversely. With the arrangement shown transverse flexing in a radial direction is accommodated more readily than transverse deflection in an axial direction due to the relative material thickness previously noted.

By virtue of the connection of the free ends 56 and fixed ends 54 of the arm portions 52, transverse deflection in a radial direction of the arm portions results in parallel linkage type of translational movement in a transverse direction which extends in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 52, which direction is substantially perpendicular to the direction of parallel linkage type translational movement provided by arm portions 36. In this regard, it will be noted that a plane passing through the axis of the intermediate member which is perpendicular to the longitudinal extent of the parallel arm portions 52 bisects the arm portions so that the amount of material in each arm portion on one side of the plane is generally equal to the amount of material on the opposite side thereof.The parallel linkage type translational movement is accomplished by a pivotal movement of the free ends 56 of the arm portions 52 by virtue of the rotatable movement of the cylindrical sections 62 of the connecting elements 66 within the cylindrical openings 58 of the free ends 56 and a flexure or material displacement of the arm portions 52 about the fixed ends 54 thereof. The pivotal connection of the connecting elements 60 with the free ends 56 enables each arm portion 52 to act in the nature of a diving board or spring board in a manner similar to arm portions 36. An arrangement of this type permits a greater degree of flexure.As before, in situations where a lesser degree of parallel misalignment is to be accommodated, the connection between the free ends of the arm portions and the connecting element can be a fixed connection, as for example, by extending a fastener radially through each fixed end and the associated connecting element.

The transverse flexure of the arm portions 52 in the axial direction accommodates an angular displacement of the axis of intermediate member 20 with respect to the axis of the second annular member 18 about an axis which extends in a direction perpendicular to the longitudinal extent of the arm portions 52. Transverse flexure of the arm portions 52 in the axial direction also accommodates axial displacement as well. Both the angular and axial displacement can take place in both directions without interference by virtue of the axial projections of the free ends 56 of the intermediate member 20.

The operation of the coupling 10 is.believed tp be evident from the description set forth above.

The parallel linkage type translational movements in two perpendicular radial directions provided by the parallel arm portions 36 and 52 serve to accommodate parallel misalignments between the shafts 12 and 14. It will be understood that during one revolution both translational movements will take place generally as out of phase sine waves when plotting translational displacement with respect to degrees of rotation.

Angular misalignment between the shafts is accommodated by the angular flexure about two transverse axes which are perpendicular and here again, during a single rotation the angular displacement in one direction has a sinusoidal amplitude which is out of phase with a similar sinusoidal amplitude of the angular displacement about the axis in the perpendicular direction.

Where axial misalignment alone is presented normally such misalignment will be accommodated by the mounting of the coupling on the shafts. However, the flexure of the arm portions enables the coupling to be mounted so that in operation an axial misalignment can be accommodated as, for example, axial shaft growth due to increased heat or operation. This is particularly important when axial misalignment is combined with parallel or angular misalignments, or both.

Figure 6 illustrates a modification in the coupling 10 which enables the same to accommodate an increased amount of axial misalignment. As shown, the modification simply involves the utilization of a pair of shoulder bolts 44' in lieu of the pair of shoulder bolts 44. Each shoulder bolt 44' includes a central cylindrical section 46', a threaded end section 48' of reduced diameter size and a head 50' of increased size in a manner similar to bolt 44.

However, the central section 46' of each bolt 44 is longer than the central section 46 of each bolt 44 thus enabling a limited amount of axial movement of the intermediate member to take place between the threaded end 48' fixed within the associated threaded opening 51 of portion 24. It will be understood that additional axial misalignment can be accommodated by similarly modifying bolts 60, although preferably only one pair is lengthened so that the other pair will tend to stabilize the position of the intermediate member 20 between the members 16 and 18 in operation.

Figure 7 discloses another desirable modification in the structure provided for effecting the rigid securement of the member 16 or 1 8 to its respective shaft as shown, member 16 is replaced by a member 16' in which the portions 28' are not drilled and tapped to receive set screws 30 as is the case with set screw receiving portions 28 of the members 16 and 18.

Instead, the third portion 26' is split radially into two sections, as indicated at 68, and a pair of bolts 70 is mounted in suitable openings 72 in the portion 26' in such a way that tightening of the bolts 70 causes the split sections of the portion 26' to move together and apply a gripping action on associated shaft onto which the member 16' has been mounted. By loosening bolts 70, the grip on the shaft is released and the member 16' can be removed from the shaft.

It will be understood that while the operation of the coupling 10 has been described in relation to a particular fixed connection with a driving shaft 12 and a driven shaft 14 the coupling is capable of similar operation when fixed in reversed arrangement to the shafts of alternatively the driven shaft becomes the driving shaft, and vice versa.

The coupling present particularly desirable and advantageous mounting characteristics with respect to shafts. First, it will be noted that the three major components of the coupling, namely the first and second annular members 1 8 and the intermediate member 20, are capable of being disassembled from operative relationship by simple removal of the four shoulder bolts. The configuration of the annular members 16 and 18 with respect to the bolts is such that axial access to the heads of the bolts can be readily obtained.

Thus, the first annular member, while including radially projecting portions 24 which receive the bolts 44 connecting the first pair of arm portions 36 therewith, is devoid of material in an axial position of alignment with the second pair of bolts 60. A similar relationship is presented with respect to the second annular member 1 8 and the bolts 44 and 60. This ready access to heads of the bolts enables the operator to conveniently use a bolt loosening and tightening tool to effect disassembly and assembly of the coupling. The mounting of the coupling to the shafts can therefore be conveniently accomplished either with the coupling 10 preassembled or disassembled, in which case assembly can be readily accomplished after the first and second annular members have been suitably fixed to their respective shafts.Moreover, this simple disassembly procedure enables an operator to quickly replace a worn-out intermediate member with a new one should the occasion demand.

The provision of a third radially projecting portion on each of the annular members 16 and 18 serves to dynamically balance these members, a desirable feature particularly in high speed applications. In the drawings the third projecting portion 26 is shown as having a threaded opening 51 similar to the threaded openings 51 formed in the portions 24. It will be understood that the openings in the portions 26 may be simply omitted. However, they are preferably provided so that where a higher degree of dynamic balancing is required shoulder bolts can be mounted therein.

Finally, it will be noted that the radially projecting configuration of the two outer annular members of the coupling provide in operation, particularly in high speed installations, a fan effect which tends to maintain the coupling in a cool running condition.

Referring now more particularly to Figures 813 of the drawings, there is shown therein a coupling of a modified form, generally indicated at 110, embodying the principles of the present invention, which has the capability of uniformly transmitting torque from a first shaft, indicated in phantom lines at 112 in Figure 8, to a second shaft, indicated at 114 in phantom lines in Figure 8, while accommodating angular and/or axial misalignment between the axes of the first and second shafts.The coupling consists essentially of three members which include first and second annular members, generally indicated at 11 6 and 118, suitably fixed to the first and second shafts 112 and 114 respectively, and an intermediate member, generally indicated at 120, disposed between the first and second annular members - 11 6 and 11 8 and operatively connected therewith.

The first and second annular members 116 and 11 8 are preferably of substantially identical construction so that a description of one will suffice to give an understanding of both.

Preferably, each of the annular members is of constant cross-sectional configuration throughout its axial extent so that each is susceptible to being initially fabricated by an extrusion process. Under these circumstances, a preferred extrusion material is aluminum or suitable alloys thereof particularly adapted for extrusion processing. It will be understood however, that while an extrudable configuration is preferred, each of the members may be machined, molded or otherwise fabricated of any other appropriate material such as ferrous metals, resinous plastics or the like.

As best shown in Figure 9, each of the annular members 11 6 and 11 8 is constructed so as to include a ring-shaped annular portion 122 having a pair of connecting element receiving portions 124 extending radially outwardly therefrom at positions spaced apart approximately 1200.In order to render each annular member symmetrical about its axis of rotation, a third portion 126 similar in configuration to the pair of portions 124 extends radially outwardly from the ring-shaped annular portion 1 22 at a position spaced apart 1 200 from each of the other two portions 1 24. In addition, each member 116 and 118 also includes three set screw receiving portions 128 which extend radially outwardly from the annular portion 1 22 to an extent considerably less than the portions 124 and 126 at positions spaced equally between the portions 124 and 1 26.

In the embodiment shown in the drawings, three set screws 1 30 are mounted so as to extend radially through the portions 128 and the adjacent sections of the annular portion 122. It will be understood that only one set screw may be provided and that such set screw may be utilized to rigidly secure a key member within a keyway formed in the interior periphery of the annular portion. Also it will be understood that any other known manner of effecting the fixed connection between each of the annular members and the associated shaft may be utilized if desired. It will be noted, however, that each mounting is such that symmetrical axis of the respective member is coincident with the axis of the shaft to which it is fixed.

The intermediate member 120 is preferably molded of a plastic material, a preferred material being polyoxymethylene resin, examples of which are available commercially under the trademarks CELCONO and DELRIN(fi). While these materials are preferred and are regarded to be quite satisfactory in operation, it will be understood that other material having the required characteristics hereinafter set forth may be utilized if desired. In the embodiment shown, the intermediate member constitutes a single molding of the aforesaid polyoxymethylene resinous material.As shown, the intermediate member includes a ring-shaped annular portion 1 32 having a cylindrical interior periphery 1 34 of a diameter size greater than the diameter size of the central shaft openings in the annular member 116and 118 so as to permit the shaft 112 and/or the shaft 114 to extend axially into the axial space occupied by the intermediate member without contacting the same while accommodating the aforesaid angular and/or axial misalignment.

The intermediate member 120 also includes a first pair of generally parallel arm portions 1 36 which are associated with the first annular member 11 6. Each of the arm portions 136 includes a fixed end 1 38 which is fixedly connected with the annular portion 1 32 within the axial extent thereof as by an integral connection.Each arm portion 1 36 also includes a free end 140 having a cylindrical opening 142 extending therethrough in a direction perpendicular to the axis of the intermediate member 1 20. Each of the free ends 140 is of generally cylindrical shape having an axial extent which is coextensive with the associated arm portion 136 and annular portion 132 and projects therebeyond in a direction toward the first annular member a short distance as, for example, approximately 1/3 to 1/2 the axial extent of the arm portion and annular portion 1 32.

The pair of free ends 140 is connected to the first pair of projecting portions 124 of the first annular member 11 6 by a pair of shoulder bolts 144. As best shown in Figures 11 and 12, shoulder bolts 144 are of generally conventional construction and include central cylindrical sections 146 having threaded sections 148 extending from one end thereof and an enlarged head 1 50 formed on the other end. The cylindrical sections engage in axially coextensive relation within the cylindrical openings 142 while the threaded sections 148 threadedly engage within threaded openings 151 extending axially through the connecting element receiving portions 124 of the first annular member 116.

It will be noted that the operative connection between the first annular member 11 6 and intermediate member 120 provided by the connecting elements 144 is related to the longitudinal extent of the pair of parallel arm portions 1 36 and the position of fixed connection of the fixed ends 1 38 thereof with annular portion 132 such as to cause torque fixedly transmitted to the first annular member 116 by the first shaft 112 to be transmitted longitudinally through one of the portions 1 36 to the annular portion 1 32 under tension and through the other arm portion 1 36 under compression. With reference to Figure 9, when annular member 116 is rotated clockwise, the arm portion 136 in the upper righthand quadrant of the Figure is in compression while the other arm portion 136 in the lower lefthand quadrant is in tension. Reversing the direction of rotation of the annular member will reverse the arm portions in compression and tension.

It will be noted that when the axes of the first and second annular members are in alignment the annular member 120 has an axis which is coincident therewith. The annular portion 132 has its axis coincident with the axis and the parallel arm portions 136 have their longitudinal extent so positioned that forces transmitted longitudinally therethrough act essentially tangentially to the axis of the intermediate member. It will also be noted that the transverse extent of each arm portion 136 measured in the radial direction is substantially less than the longitudinal extent of the arm portion but substantially greater than the transverse extent of the arm portion measured in the axial direction.Consequently, since torque transmittal from the first annular member to the intermediate member is along a line generally coincidental with the longitudinal extent of the arm portions 136 substantially no material displacement occurs by virtue of the torque transmission and hence the torque which is imparted to the first annular member 116 will likewise be uniformly transmitted to the annular portion 132 of the intermediate member. While the arm portions 136 remain rigid in the direction of torque transmission and therefore accomplish uniform torque transmission, they are rigid in a radial transverse direction and capable of flexing transversely in an axial direction.With the arrangement shown transverse flexing in a radial direction is prevented by virtue of the greater axial transverse thickness thereof while transverse deflection in an axial direction is accommodated due to the relatively thin transverse material thickness in the axial direction.

By virtue of the connection of the free ends 140 and fixed ends 138 of the arm portions 136 and the radial transverse thickness thereof, transverse deflection in a radial direction of the arm portions is prevented. The type of movement which is prevented by this rigidity is a parallel linkage type of translational movement in a transverse direction extending in a radial direction generally perpendicular to the longitudinal direction of extent of the arm portions 136. In this regard it will be noted that a plane passing through the axis of the intermediate member which is perpendicular to the longitudinal extent of the parallel arm portions 136 bisects the arm portions so that the amount of material in each arm portion on one side of the plane is generally equal to the amount of material on the opposite side thereof.In the absence of the radial rigidity provided, the parallel linkage type translational movement would be accomplished by a pivotal movement of the free ends 140 of the arm portions 136 by virtue of the rotatable movement of the cylindrical sections 146 of the connecting elements 144 within the cylindrical opening 142 of the free ends 140 and a radial flexure or material displacement of the arm portions 136 about the fixed ends 138 thereof.

The transverse flexure of the arm portions 136 in the axial direction accommodates an angular displacement of the axis of intermediate member 120 with respect to the axis of the first annular member 11 6 about an axis which extends in a direction perpendicular to the longitudinal extent of the arm portions 1 36. Transverse flexure of the arm portions 1 36 in the axial direction also accommodates axial displacement as well. Both the angular and axial displacement can take place in both directions without interference by virtue of the axial projections of the free ends 140 of the intermediate member 120.In this regard it will be noted that each of these projections may be provided by a separate washer or as part of the associated connecting element in which case the intermediate member is rendered susceptible to fabrication by extrusion techniques.

The intermediate member 120 also includes a second pair of generally parallel arm portions 1 52 disposed so that their longitudinal extent is in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 1 36. Each arm portion 152 is constructed in a manner similar to the arm portions 136 to include an integral fixed end 154 and a free end 156 having a cylindrical opening 158 extending therethrough to receive a connecting element 160. Each of the connecting elements 1 60 is of similar construction to the connecting elements 144 consisting essentially of a shoulder bolt having a cylindrical central section 1 62 with a threaded section 1 64 of reduced diameter on one end thereof and a head 1 66 on the other end thereof.The cylindrical sections 162 of the bolts 1 60 engage in axially coextensive relation within the cylindrical openings 1 58 while the threaded sections 164 threadedly engage within threaded openings extending axially through the connecting element receiving portions 124 of the second annular member 118.

It will be noted that the operative connection between the second annular member 11 8 and intermediate member 120 provided by the connecting elements 144 is related to the longitudinal extent of the pair of parallel arm portions 1 52 and the position of fixed connection of the fixed ends 1 54 thereof with annular portion 132 such as to cause torque transmitted to the annular portion through arm portions 138 to be transmitted longitudinally through one of the arm portions 1 52 to the second annular member 118 under tension and through the other arm portion 1 52 under compression.With reference to Figure 9, when the annular portion 132 of the intermediate member 120 is rotated clockwise, the arm portion 152 in the upper left-hand quadrant of the Figure is in tension while the other arm portion 152 in the lower right-hand quadrant is in compression. As before, reversing the direction of rotation of the intermediate member 120 will reverse the arm portions in compression and tension.

Again it will be noted that forces transmitted longitudinally through the arm portions 1 52 act essentially tangentially to the axis of the intermediate member 120. It will also be noted that the transverse extent of each arm portion 1 52 measured in the radial direction is substantially less than the longitudinal extent of the arm portion and substantially greater than the transverse extent of the arm portion measured in the axial direction.Consequently, since torque transmittal from the annular portion 132 to the second annular member is along a line generally coincidental with the longitudinal extent of the arm portions 1 52 substantially no material displacement occurs by virtue of this torque transmission and hence the torque which is imparted to the annular portion 132 of the intermediate member will likewise be uniformly transmitted to the second annular member 11 8.

While the arm portions 1 52 remain rigid in the direction of torque transmission and therefore accomplish uniform torque transmission, they are also operatively rigid in a radial transverse direction but capable of flexing transversely in an axial direction. With the arrangement shown transverse flexing in an axial direction is accommodated due to the relative thin material thickness previously noted while radial flexure is prevented because of the relatively greater thickness in this direction.

By virtue of the connection of the free ends 1 56 and fixed ends 154 of the arm portions 152 and the radial transverse thickness thereof, transverse deflection in a radial direction of the arm portions is prevented. This type of movement which is prevented by this rigidity is a parallel linkage type of translational movement in a transverse direction extending in a radial direction generally perpendicular to the longitudinal direction of extent of the arm portions 1 52. In this regard it will be noted that a plane passing through the axis of the intermediate member which is perpendicular to the longitudinal extent of the parallel arm portions 1 52 bisects the arm portions so that the amount of material in each arm portion on one side of the plane is generally equal to the amount of material on the opposite side thereof.In the absence of the radial rigidity provided, the parallel linkage type translational movement would be accomplished by a pivotal movement of the free ends 156 of the arm portions 152 by virtue of the rotatable movement of the cylindrical sections 162 of the connecting elements 1 66 within the cylindrical openings 1 58 of the free ends 1 56 and a radial flexure or material displacement of the arm portions 1 52 about the fixed ends 1 54 thereof.

The transverse flexure of the arm portions 1 52 in the axial direction accommodates an angular displacement of the axis of intermediate member 120 with respect to the axis of the second annular member 11 8 about an axis which extends in a direction perpendicular to the longitudinal extent of the arm portions 1 52. Transverse flexure of the arm portions 1 52 in the axial direction also accommodates axial displacement as well. Both the angular and axial displacement can take place in both directions without interference by virtue of the axial projections of the free ends 1 56 of the intermediate member 1 20.

The operation of the coupling 110 is believed to be evident from the description set forth above.

Angular misalignment between the shafts is accommodated by the angular flexure about two transverse axes which are perpendicular. It will be understood that during one revolution both translational movements will take place generally as out of phase sine waves when plotting translational displacement with respect to degrees of rotation. Thus, during a single rotation the angular displacement in one direction has a sinusoidal amplitude which is out of phase with a similar sinusoidal amplitude of the angular displacement about the axis in the perpendicular direction.

Where axial misalignment is presented normally such misalignment will be accommodated by the mounting of the coupling on the shafts. However, the flexure of the arm portions enables the coupling to be mounted so that in operation an axial misalignment combined with the angular misalignment can be accommodated as, for example, axial shaft growth due to increased heat or operation.

Figure 1 3 illustrates a modification in the coupling 110 which enables the same to accommodate an increased amount of axial misalignment. As shown, the modification simply involves the utilization of a pair of shoulder bolts 144' in lieu of the pair of shoulder bolts 144. Each shoulder bolt 144' includes a central cylindrical section 146', a threaded end section 148' of reduced diameter size and a head 150' of increased size in a manner similar to bolt 144.

However, the central section 146' of each bolt 144' is longer than the central section 146 of each bolt 144 thus enabling a limited amount of axial movement of the intermediate member to take place between the threaded end 148' fixed within the associated threaded opening 1 51 of portion 124. It will be understood that additional axial misalignment can be accommodated by similarly modifying bolts 160, although preferably only one pair is lengthened so that the other pair will tend to stabilize the position of the intermediate member 120 between the members 11 6 and 118 in operation.

Figure 14 discloses another desirable modification in the structure provided for effecting the rigid securement of the member 11 6 and 11 8 to its respective shaft as shown, member 11 6 is replaced by a member 11 6' in which the portions 128' are not drilled and tapped to receive set screws 130 as is the case with set screw receiving portions 128 of the members 116 and 118. Instead, the third portion 126t is split radially into two sections, as indicated at 168, and a pair of bolts 170 is mounted in suitable openings 1 72 in the portion i 26' in such a way that tightening of the bolts 170 causes the split sections of the portion 126' to move together and apply a gripping action on associated shaft onto which the member I 1' has been mounted. By loosening bolts 170, the grip on the shaft is released and the member 11 6' can be removed from the shaft.

It will be understood that while the operation of the coupling 110 has been described in relations to a particular fixed connection with a driving shaft 112 and a driven shaft 114 the coupling is capable of similar operation when fixed in reversed arrangement to the shafts or alternatively the driven shaft becomes the driving shaft, and vice versa.

The coupling presents particularly desirable and advantageous mounting characteristics with respect to shafts. First, it will be noted that the three major components of the coupling, namely the first and second annular members 11 8 and the intermediate member 120, are capable of being disassembled from operative relationship by the simple removal of the four shoulder bolts.

The configuration of the annular members 11 6 and 118 with respect to the bolts is such that axial access to the heads of the bolts can be readily obtained. Thus, the first annular member, while including radially projecting portions 124 which receive the bolts 144 connecting the first pair of arm portions 136 therewith, is devoid of material in an axial position of alignment with the second pair of bolts 1 60. A similar relationship is presented with respect to the second annular member 118 and the bolts 144 and 160. This ready access to heads of the bolts enables the operator to conveniently use a bolt loosening and tightening tool to effect disassembly and assembly of the coupling.The mounting of the coupling to the shafts can therefore be conveniently accomplished either with the coupling 110 preassembled or disassembled, in which case assembly can be readily accomplished after the first and second annular members have been suitably fixed to their respective shafts.

Moreover, this simple disassembly procedure enables an operator to quickly replace a worn-out intermediate member with a new one should the occasion demand.

The provision of a third radially projecting portion on each of the annular members 11 6 and 118 serves to dynamically balance these members, a desirable feature particularly in high speed applications. In the drawings the third projecting portion 126 is shown as having a threaded opening 151 similar to the threaded openings 1 51 formed in the portions 124. It will be understood that the openings in the portions 126 may be simply omitted. However, they are preferably provided so that where a higher degree of dynamic balancing is required shoulder bolts can be mounted therein.

Referring now more particularly to Figures 1 5-1 7, there is shown therein a modified form of coupling, generally indicated at 210, embodying the principles of the present invention.

The coupling 210 is similar to the coupling 110 in that it is made up of three members which include first and second annular members, generally indicated at 216 and 218, and an intermediate member, generally indicated at 220. The three members are constructed of materials and by procedures similar to those previously indicated with respect to the members 116, 118 and 120 of the coupling 110.

Each of the annular members 216 and 218 is of a construction similar to the construction of the annular members 11 6 and 118 of the coupling 110 in that each includes a ringshaped annular portion 222 having a pair of connecting element receiving portions 224 extending radially outwardly therefrom at positions spaced apart approximately 1200. As before, in order to render each annular member symmetrical about its axis of rotation a third portion 226, similar in configuration to the pair of portions 224, extends radially outwardly from the ring-shaped annular portion 222 at a position spaced apart 1200 from each of the other two portions 224.In addition, as before, each member 21 6 also includes three set screw receiving portions 228 which extend radially outwardly from the annular portion 222 to an extent considerably less than the portions 224 and 226 at positions spaced equally between the portions 224 and 226. It will also be understood that the members 216 and 218 may be secured to respective shafts in the manner previously described with respect to annular members 11 6 and 118.

The intermediate member 220, like the intermediate member 120 of coupling 110, includes a ring-shaped annular portion 232 and a first pair of generally parallel arm portions 236 associated with the first annular member 21 6.

Each of the arm portions 236 includes a fixed end 238 which is fixedly connected with the annular portion 232 within the axial extent thereof as by an integral connection. Each arm portion 236 also includes a free end 240. The configuration of each arm portion 236 is similar to the configuration of each arm portion 136 in that the transverse extent of each arm portion measured in the radial direction is substantially less than the longitudinal extent of the arm portion but substantially greater than the transverse extent of the arm portion measured in the axial direction.

The configuration provides rigidity in the direction of torque transmission, rigidity in a radial transverse direction and flexure in an axial transverse direction.

Each free end 240 is similar to each free end 140 previously described in the sense that it is cylindrical in exterior configuration. However, the axis of the cylindrical configuration extends perpendicular to the longitudinal extent of the associated arm portion within a radial plane with respect to the axis of rotation of intermediate member 220. Thus, each free end 240 is displaced 909 with respect to the corresponding free end 140 of the coupling 110. Each free end 240, like each free end 140, is formed with a cylindrical opening 242 extending axially therethrough.

The pair of free ends 240 is connected to the first pair of projecting portions 224 of the first annular member by a pair of pivot pins 244. Pivot pins 244 are suitably fixed within lug portions 246 formed integrally on the outer extremities of the connecting element receiving portion 224 and projecting axially therefrom. It will be understood that any suitable means may be provided for fixedly securing the pins 244 within the lug portions, the arrangement shown consisting of a removable bolt connection in which each pin forms a cylindrical free end portion of the shank of the bolt. This arrangement enables the three members of the coupling to be easily assembled after the annular members 216 and 218 have been suitably mounted on their respective shafts.

It will be noted that the axes of the two pivot pins 244 are coincident with respect to each other, the common axis being parallel to a common flexure axis of the pair of arm portions 236, the two common axes being equally spaced on opposite sides of a radial plane passing though the axis of rotation of the intermediate member 220 in a direction perpendicular to the longitudinal extent of the arm portions 236. It will be understood that each of the annular members 21 6 and 218 also includes a counterbalancing extension 248 on the radial extremity of the third portion 226.

It can be seen that the connection between the lug portions 246 of the first annular member 21 6 and the arm portions 236 of the intermediate member 220 provided by the pivot pins 244 enables movements and achieves functions similar to the rigid connection provided by the bolts 144 in the coupling 110. However, the pivotal connection of the pivot pins 244 within the cylindrical openings 242 in the free ends 240 enables each arm portion 236 to act in the nature of a diving board or spring board. This arrangement permits a greater degree of flexure in the arm portions 236 than is the case with the arm portions 136, both ends of which are fixed in the coupling 11 0.

The intermediate member 220 also includes a second pair of generally parallel arm portions 252 disposed so that their longitudinal extent is in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 236. As before, each of the arm portions 252 includes a fixed end 254 which is fixedly connected with the annular portion 232 within the axial extent thereof, as by an integral connection. Also as before, each arm portion 252 includes a free end 256.

The configuration of each arm portion 252 is similar to the configuration of each arm portion 1 52 in that the transverse extent of each arm portion measured in the radial direction is substantially less than the longitudinal extent of the arm portion but substantially greater than the transverse extent of the arm portion measured in the axial direction. Here again, this configuration provides rigidity in the direction of torque transmission, rigidity in a radial transverse direction and flexure in an axial transverse direction.

Each free end 256 is similar to each free end 1 56 previously described in connection with the coupling 110 in the sense that it is cylindrical in exterior configuration. However, the axis of the cylindrical configuration extends perpendicular to the longitudinal extent of the associated arm portion 252 within a radial plane with respect to the axis of rotation of the intermediate member 220. Again, as before, each free end 256 is displaced 900 with respect to the corresponding free end 1 56 of the coupling 110. Each free end 256, like each free end 156, is formed with a cylindrical opening 258 extending axially therethrough.

The pair of free ends 256 is connected to the pair of lug portions 246 of the second annular member 21 8 by a pair of pivot pins 260 which, as shown, are similar to the pins 244 and consist of a removable bolt connection in which each pin is formed as a cylindrical free end portion of the shank of the bolt.

As before, it will be noted that the axes of the two pivot pins 260 are coincident with respect to each other, the common axis being parallel to a common flexure axis of the pair of arm portions 252, the two common axes being equally spaced on opposite sides of a radial plane passing through the axis of rotation of the intermediate member 220 in a direction perpendicular to the longitudinal extent of the arm portion 252.

The connecting lug portions 246 of the second annular member 218 and the arm portions 252 of the intermediate member 220 provided by the pivot pins 260 enable movements and achieve functions similar to the rigid connection provided by the bolts 1 60 in the coupling 110. However, the pivotal connection of the pivot pins 260 within the cylindrical openings 258 in the free ends 256 enables each arm portion 252 to act in the nature of a diving board or spring board. As before, this arrangement permits a greater degree of flexure in the arm portions 252 than is the case with the arm portion 152, both ends of which are fixed in the coupling 110.

Referring now more particularly to Figures 1 8-22 of the drawings, there is shown therein a coupling, generally indicated at 310, embodying the principles of the present invention, which has the capability of resiliently transmitting torque from a first shaft, indicated in phantom lines at 312 in Figure 18, to a second shaft, indicated at 314 in phantom lines in Figure 18, while accommodating parallel, angular and/or axial misalignment between the axes of the first and second shafts.The coupling consists essentially of three members which include first and second annular members, generally indicated at 31 6 and 318, suitably fixed to the first and second shafts 312 and 314 respectively, and an intermediate member, generally indicated 320, disposed between the first and second annular members 316 and 318 and operatively connected therewith.

The first and second annular members 316 and 31 8 are preferably of substantially identical construction so that a description of one will suffice to give an understanding of both.

As best shown in Figure 19, each of the annular members 316 and 318 is constructed so as to include a ring-shaped annular portion 322 having a pair of connecting element receiving portions 324 extending radially outwardly therefrom at positions spaced apart approximately 1200. In order to render each annular member symmetrical about its axis of rotation, a third portion 326 similar in configuration to the pair of portions 324 extends radially outwardly from the ring-shaped annular portion 322 at a position spaced apart 1200 from each of the other two portions 322. In addition, each member 316 and 318 also includes three set screw receiving portions 328 which extend radially outwardly from the annular portion 322 to an extent considerably less then the portions 324 and 326 at positions spaced equally between the portions 324 and 326.

In the embodiment shown in the drawings, three set screws 330 are mounted so as to extend radially through the portions 328 and the adjacent sections of the annular portion 322. It will be understood that only one set screw may be provided and that such set screw may be utilized to rigidly secure a key member within a keyway formed in the interior periphery of the annular portion. Also it will be understood that any other known manner of effecting the fixed connection between each of the annular member and the associated shaft may be utilized if desired. It will be noted, however, that each mounting is such that the symmetrical axis of the respective member is coincident with the axis of the shaft to which it is fixed.

The intermediate member 320 is preferably molded of a plastic material, a preferred material being polyoxymethylene resin, examples of which are available commercially under the trademarks CELCONe and DELRIN9. While these materials are preferred and are regarded to be quite satisfactory in operation, it will be understood that other material having the required characteristics hereinafter set forth may be utilized if desired. In the embodiment shown, the intermediate member constitutes a single molding of the aforesaid polyoxymethylene resinous material.As shown, the intermediate member includes a ring-shaped annular portion 332 having a cylindrical interior periphery 334 of a diameter size greater than the diameter size of the central shaft openings in the annular members 31 6 and 318 so as to permit the shaft 312 and/or the shaft 314 to extend axially into the axial space occupied by the intermediate member without contacting the same while accommodating the aforesaid parallel, angular and/or axial misalignment. The intermediate member 320 also includes a first pair of generally parallel arm portions, generally indicated at 336, which are associated with the first annular member 316.Each of the arm portions 336 is formed of a pair of oppositely outwardly bowed thin central sections 337 joined at one of their ends by a fixed end 338 which is fixedly connected with the annular portion 332 within the axial extent thereof as by an integral connection. The opposite ends of the central sections 337 of each arm portion 336 are joined by a free end 340 having a cylindrical opening 342 extending therethrough in a direction perpendicular to the axis of the intermediate member 320. Each of the free ends 340 is of generally cylindrical shape having an axial extent which is coextensive with the associated arm portion 336 and annular portion 332 and projects therebeyond in a direction toward the first annular member a short distance as, for example, approximately 1/3 to 1/2 the axial extent of the arm portion and annular portion 332.

The pair of free ends 340 is connected to the first pair of projecting portions 324 of the first annular member 316 by a pair of shoulder bolts 344. As best shown in Figures 21 and 22, shoulder bolts 344 are of generally conventional construction and include central cylindrical sections 346 having threaded sections 348 extending from one end thereof and an enlarged head 350 formed on the other end. The cylindrical sections rotatably engage in axially coextensive relation within the cylindrical openings 342 while the threaded sections 348 threadedly engage within threaded openings 351 extending axially through the connecting element receiving portions 324 of the first annular member 31 6.

It will be noted that the operative connection between the first annular member 31 6 and intermediate member 320 provided by the connecting elements 344 is related to the longitudinal extent of the pair of parallel arm portions 336 and the position of fixed connection of the fixed ends 338 thereof with annular portion 332 such as to cause torque fixedly transmitted to the first annular member 316 by the first shaft 312 to be transmitted longitudinally through one of the arm portions 336 to the annular portion 332 under tension and through the other arm portion 336 under compression. With reference to Figure 19, when annular member 316 is rotated clockwise, the arm portion 336 in the upper right-hand quadrant of the Figure is in compreSsion while the other arm portion 336 in the lower left-hand quadrant is in tension.

Reversing the direction of rotation of the annular member will reverse the arm portions in compression and tension.

It will be noted that when the axes of the first and second annular members are in alignment, the annular member 320 has an axis which is coincident therewith. The annular portion 332 has its axis coincident with this axis and the parallel arm portions 336 have their longitudinal extent so positioned that forces transmitted longitudinally therethrough act essentially tangentially to the axis of the intermediate member. It will also be noted that the transverse extent of the central sections 337 of each arm portion 336 measured in the axial direction is substantially less than the longitudinal extent of the arm portion and substantially greater than the combined transverse extent of the central sections 337 of the arm portion measured in the radial direction.

Consequently, since torque transmittal from the first annular member to the intermediate member is along a line generally bisecting the longitudinal extent of the central bowed sections 337 of the arm portions 336, a limited amount of material displacement may occur which is either inwardly toward one another when under tension or outwardly away from one another when under compression. Such material displacement which results in the longitudinal expansion of the arm portion 336 which is in tension and in the compression of the other arm portion 336 generally will occur only when there is a change in the input torque transmitted. Hence, uniformly applied input torque which is imparted to the first annular member 316 will likewise be uniformly transmitted to the annular portion 332 of the intermediate member.In addition to the longitudinal resiliency of the arm portions 336 they are also capable of flexing transversely. With the arrangement shown transverse flexing in a radial direction is accommodated more readily than transverse deflection in an axial direction due to the relative material thickness previously noted.

By virtue of the connection of the free ends and fixed ends 338 of the arm portions 336, transverse deflection in a radial direction of the arm portions results in parallel linkage type of translational movement in a transverse direction which extends in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 336. In this regard it will be noted that a plane passing through the axis of the intermediate member which is perpendicular to the longitudinal extent of the parallel arm portions 336 bisects the arm portions so that the amount of material in each arm portion on one side of the plane is generally equal to the amount of material on the opposite side thereof.The parallel linkage type translational movement is accomplished by a pivotal movement of the free ends 340 of the arm portions 336 by virtue of the rotatable movement of the cylindrical sections 346 of the connecting elements 344 within the cylindrical openings 342 of the free ends 340 and a flexure or material displacement of the arm portions 336 about the fixed ends 338 thereof. The pivotal connection of the connecting elements 344 with the free ends enables each arm portion to act in the nature of a diving board or spring board. An arrangement of this type permits a greater degree of flexure.In situations where a lesser degree of parallel misalignment is to be accommodated the connection between the free ends of the arm portions and the connecting element can be a fixed connection, as for example, by extending a fastener radially through each fixed end and the associated connecting element.

The transverse flexure of the arm portions 336 in the axial direction accommodates an angular displacement of the axis of intermediate member 320 with respect to the axis of the first annular member 31 6 about an axis which extends in a direction perpendicular to the longitudinal extent of the arm portions 336. Transverse flexure of the arm portions 336 in the direction also accommodates axial displacement as well. Both the angular and axial displacement can take place in both directions without interference by virtue of the axial projections of the free ends 340 of the intermediate member 320. In this regard it will be noted that each of these projections may be provided by a separate washer or as part of the associated connecting element in which case the intermediate member is rendered susceptible to fabrication by extrusion techniques.

The intermediate member 320 also includes a second pair of generally parallel arm portions, generally indicated at 352, disposed so that their longitudinal extent is in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 336. Each arm portion 352 is constructed in a manner similar to the arm portions 336 to include a pair of oppositely outwardly bowed central sections 353 integrally joined by an integral fixed end 354 and a free end 356 having a cylindrical opening 358 extending therethrough to receive a connecting element 360. Each of the connecting elements 360 is of similar construction to the connecting elements 344 consisting essentially of a shoulder bolt having a cylindrical central section 362 with a threaded section 364 of reduced diameter on one end thereof and a head 366 on the other end thereof. The cylindrical section 362 of the bolts 360 rotatably engage in axially coextensive relation within the cylindrical openings 358 while the threaded sections 364 threadedly engage within threaded openings extending axially through the connecting element receiving portions 324 of the second annular member 318.

It will be noted that the operative connection between the second annular member 318 and intermediate member 320 provided by the connecting elements 344 is related to the longitudinal extent of the pair of parallel arm portions 352 and the position of fixed connection of the fixed ends 354 thereof with annular portions 332 such as to cause torque transmitted to the annular portion through arm portions 338 to be transmitted longitudinally through one of the arm portions 352 to the second annular member 31 8 under tension and through the other arm portion 352 under compression. With reference to Figure 19, when the annular portion 332 of the intermediate member 320 is rotated clockwise, the arm portion 352 in the upper lefthand quadrant of the Figure is in tension while the other arm portion 352 in the lower right-hand quadrant is in compression.As before, reversing the direction of rotation of the intermediate member 320 will reverse the arm portions in compression and tension.

Again it will be noted that forces transmitted longitudinally th rough the arm portions 352 act essentially tangentially to the axis of the intermediate member 320. It will also be noted that the transverse extent of each arm portion 352 measured in the axial direction is substantially less than the longitudinal extent of the arm portion and substantially greater than the combined transverse extent of the central sections of the arm portion measured in the radial direction. Consequently, since torque transmitted from the annular portion 332 to the second annular member is along a line bisecting the longitudinal extent of the central bowed sections 353 of the arm portions 352, a limited amount of material displacement can occur by virtue of changes in this torque transmission.However, uniformly applied input torque which is imparted to the annular portion 332 of the intermediate member will be uniformly transmitted to the second annular member 31 8. As before, in addition to longitudinal extension or contraction of the arm portion 352, they are also capable of flexing transversely. With the arrangement shown transverse flexing in a radial direction is accommodated more readily than transverse deflection in an axial direction due to the relative material thickness previously noted.

By virtue of the connection of the free ends 356 and fixed ends 354 of the arm portions 352, transverse deflection in a radial direction of the arm portions results in parallel linkage type of translational movement in a transverse direction which extends in a direction generally perpendicular to the longitudinal direction of extent of the arm portions 352, which direction is substantially perpendicular to the direction of parallel linkage type translational movement provided by arm portions 336. In this regard it will be noted that a plane passing through the axis of the intermediate member which is perpendicular to the longitudinal extent of the parallel arm portions 352 bisects the arm portions so that the amount of material in each arm portion on one side of the plane is generally equal to the amount of material on the opposite side thereof.The parallel linkage type translational movement is accomplished by a pivotal movement of the free ends 356 of the arm portions 352 by virtue of the rotatable movement of the cylindrical sections 362 of the connecting elements 366 within the cylindrical openings 358 of the free ends 356 and a flexure or material displacement of the arm portions 352 about the fixed ends 354 thereof.

The pivotal connection of the connecting elements 360 with the free ends 356 enables each arm portion 352 to act in the nature of a diving board or spring board in a manner similar to arm portions 336. An arrangement of this type permits a greater degree of flexure. As before, in situations where a iesser degree of parallel misalignment is to be accommodated, the connection between the free ends of the arm portions and the connecting element can be a fixed connection, as for example, by extending a fastener radially through each fixed end and the associated connecting element.

The transverse flexure of the arm portions 352 in the axial direction accommodates an angular displacement of the axis of intermediate member 320 with respect to the axis of the second annular member 31 8 about an axis which extends in a direction perpendicular to the longitudinal extend of the arm portions 352. Transverse flexure of the arm portions 352 in the axial direction also accommodates axial displacement as well. Both the angular and axial displacement can take place in both directions without interference by virtue of the axial projections of the free ends 356 of the intermediate member 320.

The operation of the coupling 310 is believed to be evident from the description set forth above.

So long as the input torque from the input shaft is uniform, uniform torque will be transmitted to the output shaft 314 and the arm portions 336 and 352 will remain in a fixed position of extension or contraction, depending upon whether the forces transmitted by the respective arm portions are tensile or compressive and the magnitude of such forces. When a change in the input torque occurs, the arm portions are capable of further extension or contraction to resiliently absorb the change in torque. In this way the coupling serves to dampen out abrupt torque changes which is a desirable characteristic in many applications.It will be noted that the longitudinal flexibility or resilience of the arm portions 336 and 352 is limited by the arm portions in tension being displaced until the normally outwardly bowed central sections 337 thereof are displaced inwardly into a position parallel with one another and parallel with the longitudinal bifurcating axis of the associated arm portion. Consequently it will be understood that the arm portion configuration thus far described provides only a limited amount of longitudinal displacement.

The parallel linkage type translational movements in two perpendicular radial directions provided by the parallel arm portions 336 and 352 serve to accommodate parallel misalignments between the shafts 312 and 314.

It will be understood that during one revolution both translational movements will take place generally as out of phase sine waves when plotting translational displacement with respect to degrees of rotation. Angular misalignment between the shafts is accommodated by the angular flexure about two transverse axes which are perpendicular and here again, during a single rotation the angular displacement in one direction has a sinusoidal amplitude which is out of phase with a similar sinudoidal amplitude of the angular displacement about the axis in the perpendicular direction. Where axial misalignment alone is presented normally such misalignment will be accommodated by the mounting of the coupling on the shafts.However, the flexure of the arm portions enables the coupling to be mounted so that in operation an axial misalignment can be accommodated as, for example, axial shaft growth due to increased heat or operation. This is particularly important when axial misalignment is combined with parallel or angular misalignments, or both.

Figure 23 illustrates a modification in the coupling 310 which enables the same to accommodate an increased amount of axial misalignment. As shown, the modification simply involves the utilization of a pair of shoulder bolts 344' in lieu of the pair of shoulder bolts 344. Each shoulder bolt 344' includes a central cylindrical section 346', a threaded end section 348' of reduced diameter size and a head 350' of increased size in a manner similar to bolt 344.

However, the central section 346' of each bolt 344' is longer than the central section 346 of each bolt 344, thus enabling a limited amount of axial movement of the intermediate member to take place between the threaded end 348' fixed within the associated threaded opening 351 of portion 324. It will be understood that additional axial misalignment can be accommodated by similarly modifying bolts 60, although preferably only one pair is lengthened so that the other pair will tend to stabilize the position of the intermediate member 320 between the members 316 and 318 in operation.

Figure 24 discloses another desirable modification in the structure provided for effecting the rigid securement of the member 316 or 31 8 to its respective shaft as shown, member 316 is replaced by a member 31 6' in which the portions 328' are not drilled and tapped to reeive set screws 330 as is the case with set screw receiving portions 328 of the member 31 6 and 318. Instead, the third portion 326' is split radially into two sections, as indicated at 368, and a pair of bolts 370 is mounted in suitable openings 372 in the portion 326' in such a way that tightening of the bolts 370 causes the split sections of the portion 326' to move together and apply a gripping action on associated shaft onto which the member 316' has been mounted.By loosening bolts 370, the grip on the shaft is released and the member 316' can be removed from the shaft.

Figures 25 and 26 illustrate a modification in the intermediate member 320 of the coupling 310 which is designated by the reference numeral 320'. In the member 320' the arm portions 336' and 352' thereof are formed with a modified construction providing for a relatively greater amount of longitudinal displacement than relatively limited displacement of the arm portions 336 and 352 previously described. As shown the arm portions 336 instead of being formed with oppositely outwardly bowed central sections 337, are each formed with a central section 374 which is of sine wave configuration. Likewise, the arm portions 352' include sine wave shaped central sections 376. As shown, the sine wave configurations of the arm portions of each pair bear a mirror image relationship with respect to one another.With this arrangement, the limiting factor in longitudinal displacement is the amount of compression which can occur rather than the amount of extension, as with the arm portions 336 and 352. It will be understood that the intermediate member 320' includes all of the other configurations embodied in the intermediate member 320 and corresponding portions are designated by corresponding prime numerals. Likewise, the intermediate member 320' is assembled in the coupling in the same fashion as the intermediate member 320.

It will be understood that while the operation of the coupling 310 has been described in relation to a particular fixed connection with a driving shaft 312 and a driven shaft 314, the coupling is capable of similar operation when fixed in reversed arrangement to the shafts or alternatively the driven shaft becomes the driving shaft, and vice versa.

The coupling presents particularly desirable and advantageous mounting characteristics with respect to shafts. First, it will be noted that the three major components of the coupling, namely the first and second annular members 318 and the intermediate member 320, are capable of being disassembled from operative relationship by the simple removal of the four shoulder bolts.

The configuration of the annular members 316 and 31 8 with respect to the bolts is such that axial access to the heads of the bolts can be readily obtained. Thus, the first annular member, while including radially projecting portions 324 which receive the bolts 344 connecting the first pair of arm portions 336 therewith, is devoid of material in an axial position of alignment with the second pair of bolts 360. A similar relationship is presented with respect to the second annular member 318 and the bolts 344 and 360. This ready access to heads of the bolts enables the operator to conveniently use a bolt loosening and tightening tool to effect disassembly and assembly of the coupling. The mounting of the coupling to the shafts can therefore be conveniently accomplished either with the coupling 310 preassembled or disassembled, in which case assembly can be readily accomplished after the first and second annular members have been suitably fixed to their respective shafts.

Moreover, this simple disassembly procedure enables an operator to quickly replace a worn-out intermediate member with a new one should the .occasion demand.

The provision of a third radially projecting portion on each of the annular members 316 and 318 serves to dynamically balance these members, a desirable feature particularly in high speed applications. In the drawings the third projecting portions 326 is shown as having a threaded opening 351 similar to the threaded openings 351 formed in the portions 324. It will be understood that the openings in the portions 326 may be simply omitted. However, they are preferably provided so that where a higher degree of dynamic balancing is required shoulder bolts can be mounted therein.

It thus will be seen that the objects of this invention have been fully and effectively accomplished. It will be realized, however, that the foregoing preferred specific embodiment has been shown and described for the purpose of illustrating the functional and structural principles of this invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.

Claims

1. A coupling for transmitting torque from a first shaft to a second shaft while accommodating parallel, angular and/or axial misalignment between the axes of said first and second shafts, said coupling comprising: a first annular member having means for fixedly securing the same to the first shaft for rotation therewith about an axis of rotation coincident with the axis of the first shaft, a second annular member having means for fixedly securing the same to the second shaft for rotation therewith about an axis of rotation coincident with the axis of the second shaft, a third intermediate member having an axis of rotation aligned with the axes of rotation of said first and second annular members when the axes of the latter are aligned, said intermediate member including an annular portion disposed between said first and second annular members and first and second pairs of elongated generally parallel arm portions operatively associated with said first and second annular members respectively, each of said arm portions including a fixed end fixedly inter connected with said annular portion within the axial extent thereof and a free end, a first pair of connecting elements fixedly projecting axially from said first annular member and connected with the free ends of said first pair of parallel arm portions at positions related to the longitudinal extent of said first pair of parallel arm portions and the position of fixed connection of the fixed ends thereof with said annular portion so as to cause torque fixedly transmitted to said first annular member by the first shaft to be transmitted longitudinally through one of said first pair of arm portions to said annular portion under tension and through the other of said first pair of arm portions to said annular portion under compression while enabling through transverse material flexure of said first pair of arm portions the following relative motions of said annular portion with respect to said first annular member, (1) an angular movement about an axis extending generally in said first transverse direction, and (2) an axial movement, and a second pair of connecting elements projecting axially from said second annular member and connected with the free ends of said second pair of parallel arm portions at positions related to the longitudinal extent of said second pair of parallel arm portions and the position of fixed connection of the fixed ends thereof with said annular portion so as to cause torque transmitted to said annular portion to be transmitted longitudinally through one of said second pair of arm portions to said second annular member under tension and through the other of said second pair of arm portions to said second annular member under compression while enabling through transverse material flexure of said second pair of arm portions the following relative motions of said annular portion with respect to said second annular member: (1) an angular movement about an axis extending generally in said second transverse direction, and (2) an axial movement.

2. A coupling as defined in claim 1 wherein each of said first pair of parallel arm portions are structured to enable through transverse material flexure a third relative motion of said annular portion with respect to said first annular member which is a parallel linkage type substantially rectilinear movement in a first transverse direction generally perpendicular to the longitudinal extent of said first pair of parallel arm portions and said second pair of parallel arm portions are structured to enable through transverse material flexure a third relative motion of said annular portion with respect to said second annular member which is a parallel linkage type substantially rectilinear movement in a second transverse direction generally perpendicular to the longitudinal extent of said second pair of parallel arm portions and said first transverse direction.

3. A coupling as defined in claim 1 or 2 wherein each of said arm portions is structured to transmit torque longitudinally therethrough whether in tension or compression without longitudinal material displacement whereby said coupling transmits the torque from said first shaft to said second shaft uniformly.

4. A coupling as defined in claim 1,2 or 3 wherein each of said first and second annular members includes an annular hub portion and a pair of connecting element receiving portions extending radially outwardly at approximately 1200 from one another.

5. A coupling as defined in claim 4 wherein said first annular member is configured to be symmetrical about its axis and to be devoid of material at positions aligned axially with said second pair of connecting elements when the axes of all of said annular members are aligned, said second annular member being configured to be symmetrical about its axis and to be devoid of material at positions aligned axially with said first pair of connecting elements when the axes of all of said annular members are aligned.

6. A coupling as defined in claim 5 wherein each of said first and second annular members includes a third portion of a configuration similar to said pair of connecting element receiving portions extending radially outwardly from said annular hub portion at a position approximately 1200 from each of said pair of connection element receiving portions.

7. A coupling as defined in claim 6 wherein said first and second annular members include three set screw receiving portions extending radially outwardly from said hub portion to an extent substantially less than said connecting element receiving portions at positions spaced equally between the latter and said third portion.

8. A coupling as defined in claim 7 wherein each of said first and second annular members is of uniform cross-sectional configuration throughout the axial extent thereof.

9. A coupling as defined in claim 1,2, 3, 4, 5, 6, 7 or 8 wherein the annular portion and arm portions of said intermediate member are integrally molded of polyoxymethylene resin.

10. A coupling as defined in claim 9 wherein the annular portion of said intermediate member is of ring-shaped configuration symmetrical about the axis of said intermediate member, said first pair of parallel arm portions containing a substantially equal amount of material in the sections thereof disposed on opposite sides of a plane passing through the axis of said intermediate member and extending in said first transverse direction, said second pair of parallel arm portions containing a substantially equal amount of material on opposite sides of a plane passing through the axis of said intermediate member and extending in said second transverse direction.

11. A coupling as defined in claim 10 wherein the central section of each arm portion between the fixed end and the free end thereof has a transverse extent measured in the axial direction which is substantially less than its longitudinal extent and substantially greater than its transverse extent measured in the radial direction.

12. A coupling as defined in claim 11 wherein the free ends of said first pair of arm portions extend axially in a direction toward said first annular member beyond the remainder thereof which is axially coextensive with said annular portion, the free ends of said second pair of arm portions extending axially in a direction toward said second annular member beyond the remainder thereof which is axially coextensive with said annular portion.

13. A coupling as defined in claim 9 wherein each of said connecting elements comprises a shoulder bolt having a central cylindrical section of an intermediate size rotatably engaged within a cylindrical opening in the associated arm portion free end, a threaded section of reduced size on one end of said central section fixedly engaged within a threaded opening in the associated annular member and a head of enlarged size on the opposite end of said central section.

14. A coupling as defined in claim 1 3 wherein the axial extent of the central cylindrical section of each bolt constituting at least one pair of said connecting elements exceeds the axial extent of the cylindrical opening within which it is rotatably engaged.

1 5. A coupling as defined in claim 9 wherein the interior periphery of said ring-shaped annular portion is of a diameter size sufficiently greater than the diameter size of the first shaft or the second shaft so that either or both of the latter may extend axially into the axial space occupied by said intermediate member without contacting the same while accommodating the aforesaid parallel, angular and/or axial misalignment.

1 6. A coupling as defined in claim 1,2, 3, 4, 5, 6, 7 or 8 wherein each of said connecting elements comprises a shoulder bolt having a central cylindrical section of an intermediate size rotatably engaged within a cylindrical opening in the associated arm portion free end, a threaded section of reduced size on one end of said central section fixedly engaged within a threaded opening in the associated annular member and a head of enlarged size on the opposite end of said central section.

17. A coupling as defined in claim 1 5 wherein the axial extent of the central cylindrical section of each bolt constituting at least one pair of said connecting elements exceeds the axial extent of the cylindrical opening within which it is rotatably engaged.

18. A coupling as defined in claim 1, 2, 3, 4, 5, 6, 7 or 8 wherein the annular portion of said intermediate member is of ring-shaped configuration symmetrical about the axis of said intermediate member, said first pair of parallel arm portions containing a substantially equal amount of material in the sections thereof disposed on opposite sides of a plane passing through the axis of said intermediate member and extending in said first transverse direction, said second pair of parallel arm portions containing a substantially equal amount of material on opposite sides of a plane passing through the axis of said intermediate member and extending in said second transverse direction.

1 9. A coupling as defined in claim 18 wherein the central section of each arm portion between the fixed end and the free end thereof has a transverse extent measured in the axial direction which is substantially less than its longitudinal extent and substantially greater than its transverse extent measured in the radial direction.

20. A coupling as defined in claim 1 9 wherein the free ends of said first pair of arm portions extend axially in a direction toward said first annular member beyond the remainder thereof which is axially coextensive with said annular portion, the free ends of said second pair of arm portions extending axially in a direction toward said second annular member beyond the remainder thereof which is axially coextensive with said annular portion.

21. A coupling as defined in claim 5 wherein the shaft securing means of said first and second members each is provided by radially splitting the third portion of the associated member into two sections and mounting bolt means therein capable of moving the two split sections together so as to cause the associated member to rigidly grip the associated shaft on which it is mounted.

22. A coupling for transmitting torque between two shafts comprising two annular members, each for connection to one of the shafts and an intermediate member also of annular form connecting the two annular members, the intermediate member having two pairs of generally parallel arm portions and each annular member having a pair of axially extending connecting elements each connected to the free end of one arm portion of an associated pair of the arm portions.

23. A coupling for transmitting torque between two shafts substantially as described herein with reference to the drawings.