Abstract:
The invention relates to a torsionally rigid, play-free, metal bellows-type, flexible shaft coupling for the torque-transmissive interconnection of two shafts. A metal bellows ( 1 ) has its generally axially flanged-out ends ( 1 ′) clamped on the ends of shafts ( 4 ) for frictional engagement. For the provision of a torsionally rigid, torsionally play-free and flexible coupling which can be manufactured inexpensively, which is readily available due to a modular design and which does not affect the drive train dynamics, the ends ( 1 ′) of metal bellows ( 1 ) have clamping rings ( 2, 2   a ) placed thereon which have slots ( 2 ′) therein and are adapted to be compressed by the width of slot ( 2 ′) to preferably directly clamp the ends ( 1 ′) of metal bellows ( 2 ) down on shafts ( 4 ).

Description:
FILED OF THE INVENTION 
     The invention relates generally to a torsionally rigid, play-free, metal bellows-type flexible coupling for the torque-transmitting connection of two shafts, and more specifically to such a coupling capable of providing a rigid, play-free coupling between two shaft ends in which the shaft diameters may be of different sizes. 
     BACKGROUND ART 
     For connecting the metal bellows with the input and output shafts so that no torsional play can exist, the state of the art calls for two interfaces or joints, namely, one between the bellows and a hub and the other between that hub and the shaft. One drawback of the prior interfaces or joints is that they cannot be separated in a non-destructive manner—such as welds provided in accordance with a variety of processes, joints using one, two or more adhesive bonds, or beads and flanges. For the second interface or joint between the hub and the shaft, conical connections, shrink washers, collets or radially clamping hubs have been used in the past. 
     In the prior bellows-type couplings, the necessity of providing two interfaces or joints causes the following drawbacks: high cost of fabrication, insufficient flexibility when adapting the coupling to the customers&#39; interface or connecting positions, and a high mass inertia due to the great number of components. 
     SUMMARY OF THE INVENTION 
     Where it is necessary to quickly provide a low-cost, torsionally rigid, elastic compensating coupling, an ideal coupling design would have to have the following advantages: 
     Combination of the two interfaces or joints to form one interface or joint; modular construction; adaptability to compensate existing shaft misalignment by simple replacement of the torque-transmitting metal bellows; torsionally play-free design; high torsional rigidity; low rigidity to displacement; low mass moment of inertia. 
     In order to obtain all the aforesaid advantages, the object underlying the invention is seen in the provision of a metal bellows-type compensating coupling which is inexpensive to manufacture, is modular to enhance its availability, is torsionally rigid and torsionally play-free and elastic, and in the installed condition does not substantially affect drive train dynamics. 
     This object is achieved by means of the characterizing features specified in the description below. 
     The principle underlying the invention is the functional combination of the frictional connections between the bellows and the hub and between the hub and the shaft to form a single joint, with the cylindrical or inwardly slightly tapered end of the bellows frictionally engaged with the input and output shaft directly or indirectly by means of an external clamping unit. 
     DISCUSSION OF THE PRIOR REFERENCES 
     East German patent DD 147 742 discloses a metal bellows-type coupling in which the end of the metal bellows is flanged out in a generally axial direction (slightly tapered or cylindrical with a crimp) and is placed over a hub on the shaft. An external member not described in detail is used to clamp the end down on the hub and thus on the shaft. 
     DE-A-42 17 764 shows a metal bellows-type coupling in which a radially slotted clamping ring—compressible by the width of the slot—is used to clampingly engage the metal bellows with the shafts. The manner of connecting the metal bellows with the clamping ring is not described in detail; also, it engages the shaft directly. 
     According to the disclosure of U.S. Pat. No. 3,232,076, a metal bellows-type coupling is provided with a metal bellows axially cylindrically flanged out at its ends, said ends being introduced in recesses machined in internally tapered threaded sleeves. These sleeves receive external nuts which are oppositely tapered internally. The tapered bores receive an axially slitted double cone surrounding the shaft. Tightening the nut causes the double cone to be compressed radially and to be clamped down on the shaft. 
     The metal bellows coupling of U.S. Pat. No. 4,645,473 comprises a metal bellows with cylindrically flanged ends each seated on a ring. Adjoining the rings are axially hollow, longitudinally slitted sleeves having tapered outer threads thereon, said rings being placed on the shafts; tightening the threaded sleeves will radially compress them to clamp the metal bellows onto the shaft. 
     The journal “Antriebstechnik” 1997, issue no. 10, page 88, discloses a metal bellows-type coupling comprising a unit assembled of the metal bellows and a hub adhesively bonded thereto, said unit being placed on a hub connected with the shaft. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following text describes exemplary embodiments of the invention, making reference to the attached drawings. 
     FIG. 1 shows a longitudinal section of a first embodiment of the invention; 
     FIG. 1 a  shows-partially in section an associated clamping ring; 
     FIG. 2 shows a longitudinal section of a second embodiment of the invention; 
     FIGS. 3 a  and  3   b  respectively, show a plan view and a side view partially in section of an associated clamping ring; 
     FIGS. 4 a  and  4   b  respectively, show a first embodiment of a reducing sleeve for cylindrical shafts; 
     FIGS. 5 a  and  5   b  respectively, show a second embodiment of a reducing sleeve for tapered shafts; 
     FIG. 6 shows a retaining spring; and 
     FIG. 7 is a cross-sectional view of a metal bellows according to the present invention prior to insertion into a clamping ring. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, two shafts  14  are interconnected at their ends for torque transmission by means of a metal bellows  10 . To this end, metal bellows  10  has flanged-out ends  12  to frictionally engage shafts  14 . Flanged-out ends  12  may be cylindrical or slightly inwardly conical or tapered, and they may include optional longitudinal slits therein. The first embodiment is recommended for use on cylindrical ends  12  the second on slightly inwardly conical ends  12 ; the last-mentioned shape enhances the frictional engagement. 
     Ends  12  of metal bellows  10  are clamped down on shafts  14  by external clamping means, which are shown here to comprise clamping rings  20 . As shown in FIG. 1 a , clamping ring  20  includes a central bore  23 , and is radially slotted at a desired position and can be compressed by the width of slot  22 . Preferably the slot  22  is slightly wider than is necessary to enable the required compression to allow for wear, for oval deformation of the clamping ring  20 , and for slightly differing shaft diameters. 
     Clamping ring  20  comprises a suitably flexible elastic or resilient material, preferably a metal, such as spring steel. Compression is effected by a clamping screw  24  disposed in aligned bores in the two ends of the clamping ring  20 , with the cylindrical bore  26  receiving the head and an internally threaded bore  28  receiving the threaded portion of the clamping screw  24 . This ensures a torque-transmitting frictional engagement of metal bellows  10  with the ends of shafts  14 . 
     FIG. 2 shows an embodiment of the invention  30  particularly suited for the coupling of shafts of different diameters. It also has the ability to couple parallel shafts to conical shafts (not shown in FIG. 2) by the use, respectively, of reducing sleeves  32 ,  34  disposed between the shafts and the flanged out ends  36 ,  38  of the metal bellows  10 . The coupling of FIG. 2 has at its left end a reducing sleeve  32  which is shown in more detail in FIGS. 4 a  and  4   b  to make up the difference in diameter between the flanged out end  36  and a parallel shaft (not shown) entering the coupling  30  of FIG. 2 from the left-hand side. The left-hand flanged out end  36  of the metal bellows  10  is clamped down onto the reducing sleeve  32  by a clamping ring  40 , which is tightened in the manner described with reference to the embodiment of FIG.  1 . If it is desired to join two parallel shafts, then both the right and the left-hand end of the coupling shown in FIG. 2 can have similar reducing sleeves  32 . Reducing sleeves  32 ,  34  of different internal diameters can enable the coupling of parallel shafts of different diameters. 
     The right-hand end of the coupling shown in FIG. 2 has a reducing sleeve  34  with a conical inner bore  42 , more clearly shown in FIGS. 5 a  and  5   b . Such a bore  42  can typically be a “morse” taper or have a key way  44  as shown in FIGS. 5 a  and  5   b . The flanged out end  38  of the metal bellows  10  at the right-hand end of FIG. 2 is clamped down onto the reducing sleeve  34  by means of a clamping ring  46  which can be tightened in the same way as the embodiment shown in FIG.  1 . In this case however, the shaft (not shown) entering from the right-hand side of the coupling  30  in FIG. 2 is secured in the conical bore  42  by virtue of the cone and therefore the clamping force does not need to be communicated through the reducing sleeve  34 . The reducing sleeve  34  thus effectively becomes part of the shaft  14 . Each of the clamping rings  40 ,  46  shown in FIG. 2 has within its bore  23  and positioned near to the end face, an annular groove  60 . This groove  60  aligns with a corresponding groove  62 ,  64  (FIGS. 4 b ,  5   b ) in the reducing sleeve  32 ,  34  and together hold a spring clip  50  (also shown in FIG.  6 ), which extends into the central bore  23  and is received in radial inner groove  60  in the clamping ring for radially fixing the clamping ring and reducing sleeve in place, and serves to prevent axial movement of the reducing sleeve  32 ,  34  with respect to the clamping rings  40 ,  46  before the clamping rings  40 ,  46  are tightened down. 
     FIGS. 3 a  and  3   b  show a clamping ring either ring  40  or ring  46 , in more detail. The arrangement for tightening the clamping ring is however not shown in the left-hand diagram of FIG. 3 a , but is the same as the arrangement shown in FIG.  2 . The right-hand diagram of FIG. 3 b  shows the radial extending annular groove  60  for reception of the retaining spring clip  50  disposed close to the right-hand outerface of the clamping ring  46 . The inner face is provided with an internal bevel to clear the radius where the flanged out end  38  of the metal bellows  10  merges into the central bellows section. 
     FIGS. 4 a  and  4   b  show in more detail the reducing sleeve  32 . This has a central bore for receiving the parallel shaft and axially extending lots  66 . These slots  66  are disposed at 90° spacing around the circumference of the sleeve  32  and extend into the bore. They are machined alternately from opposing end faces of the sleeve  32 . The slots  66  provide a radial resilence enabling force exerted by the clamping ring  40  to be transmitted through to the cylindrical shaft (not shown) thus holding the entire assembly rigid. This clamps the flanged out ends  36  (FIG. 2) of the metal bellows  10  between the clamping ring  40  and the reducing sleeve  32  and between the reducing sleeve  32  and the cylindrical shaft (not shown). An annular groove  62  (FIG. 4 b ) is shown in the cylindrical outer surface of the reducing sleeve  32  to accept the retaining spring clip  50  shown in FIG.  6 . 
     As shown in FIGS. 5 a  and  5   b , there is provided an internally conical reducing sleeve  34  with an internal key way  44  for securing on shaft  14  (FIG.  1 ); a radially extending circumferential groove  64  is machined in the external diameter in order to receive and hold retaining spring clip  50  (FIG. 6) in place. 
     FIG. 6 shows the retaining spring clip  50 , which preferably is polygonal in shape. It may be made of spring steel wire. The spring clip  50  is triangular, but square or pentagonal springs are also possible. The polygonal shape helps concentrate the force of the spring onto distinct sections of the spring, i.e., the center of the sides, and leaves corners of the spring protruding from groove  60  (FIG. 3) for ease of assembly, disassembly and engagement with the slot in the clamping ring. The presence of the spring clip  50  gives rise to a snap action as the device is assembled. This assures the operator that the assembly is in a position for tightening. 
     An alternative arrangement to the clamping rings  40  and  46  described with respect to FIGS. 1 and 2 is to use a commercially available shrink washer (not shown), which directly clamps the ends  36 ,  38  of the metal bellows  10  down onto the shafts  14 . 
     FIG. 7 is a cross-sectional view of a metal bellows  110  according to the present invention prior to it insertion into a clamping ring. Metal bellows  10  includes flanged out ends  136 ,  138 , one at either axial end of the metal bellows, similar to metal bellows  10  of FIGS. 1 and 2. Flanged out ends  136 ,  138  each have at least one, and preferably two axial slots  140  so as to permit some radial flexure to the flanged out ends  136 ,  138 . Flanged out ends  136 ,  138  in this embodiments has a shape that is slightly inwardly conical, shown in greatly exaggerated from in FIG. 1, so that the surface of the flanged out ends  136 ,  138  converge toward the centerline in the direction of the metal bellows.