Patent Document

[0001]    This application is based on and claims priority under 35 U.S.C. §119 with respect to Swedish Application No. 0101444-8 filed on Apr. 23, 2001, the entire content of which is incorporated herein by reference.  
         FIELD OF THE INVENTION  
         [0002]    The present invention generally relates to devices for arresting an element on a shaft. More particularly, the present invention pertains to an attachment mechanism intended for arresting a machine member, such as a pulley, a sheave, a sprocket or the like, on a cylindrical shaft.  
         BACKGROUND OF THE INVENTION  
         [0003]    The mounting of elements such as sheaves, sprockets or the like on a cylindrical shaft so that the element is arrested against circumferential and/or axial movements relative to the shaft can be effected in different ways. One example is to provide a keyway in the shaft and/or in the boss or hub of the machine member, and a key inserted in the keyway for preventing relative circumferential movement. However, this arresting mechanism requires a more expensive machining of the keyway in the shaft, reduces the strength of the shaft and is not well suited to being used together with relatively light and inexpensive hollow shafts.  
           [0004]    Similar limitations can be seen with use of threaded joints as this requires thread cutting of the shaft and inner surface of the bore in the machine member.  
           [0005]    Cylindrical shaft and hub joints can also be obtained with a press fit effected with or without the use of a pressure oil arrangement. However, with these mechanisms, it is also difficult to use hollow shafts due to large radially inwardly directed forces.  
           [0006]    Swedish Patent Application No. 9901711-3 discloses an attachment mechanism intended for arresting a machine member having a substantially cylindrical bore on a cylindrical shaft. The bore has a larger inner diameter than the outer diameter of the shaft to provide an annular space between the machine member and the shaft. In this space is inserted a pair of elements having mating, cooperating taper surfaces facing each other, with the elements being intended at mutual displacement to change their overall radial size, thereby increasing or reducing the clamping force between the machine member and the shaft. The elements are in the form of a first thin-walled sleeve member having a smooth inner surface arranged to enclose a portion of the shaft, and a second thin-walled sleeve member having a smooth outer surface arranged to engage the bore of the machine member, with the second sleeve member enclosing the first sleeve member. The first and second sleeve members in their surfaces that face each other have a plurality of saw-tooth-shaped consecutive axially tapering sections. In addition, one of the end edges of the second sleeve member abuts against a stop provided in the machine member, and the first sleeve member projects outside the opposite end edge of the second sleeve member for being readily accessible to receive an external pushing force causing such mutual displacement between the first and second sleeve members.  
           [0007]    This generally described attachment mechanism is able to function relatively well, but suffers from the drawback that the size relationship between the shaft and bore of the sheave is very important for allowing proper attachment to be obtained. This makes it necessary to provide a substantial number of differently sized sleeve members.  
           [0008]    [0008]FIG. 1 shows in cross-section an attachment device similar to that described above and disclosed in Swedish patent application No. 9901711-3. In this known device, a machine member  11  is secured to a portion of a hollow shaft  10 . The machine member  11  is shown only partially and is in the form of a sheave. As shown, the hollow shaft  10  has a cylindrical external peripheral surface and the machine member  11  has an inner bore of cylindrical shape, with the inner diameter of the bore in the machine member  11  exceeding the outer diameter of the shaft  10 . A shoulder  12  is provided at one axial side of the bore in the machine member  11 . This shoulder  12  has a diameter slightly larger than the outer diameter of the shaft  10 , thereby providing a clearance so that the machine member  11  can be easily pushed up the shaft  10  to a desired arresting position. The annular space  13  formed between the inner surface of the bore in the machine member  11  and the outer peripheral surface of the shaft  10  has a certain radial dimension x. In this space is inserted the primary part of the attachment mechanism which is in the form of the two-piece sleeve  15 .  
           [0009]    This two-piece sleeve  15  includes a first or inner sleeve piece  15   a  having a cylindrical inner surface and an external surface provided with a continuous axially arranged series of tapering, substantially saw-tooth-shaped surface elements, in which a first surface element b tapers from a larger diameter to a smaller diameter, followed by a consecutive second surface element c connected to the first surface element b via a substantially radial wall member d so that the end of the second surface element c adjacent the narrower end of the first surface element b has substantially the same outer diameter as that of the first surface element b at its largest end, i.e. at the end remote from the second surface element c. The second surface element c is related to and connected to the consecutive next surface element e in the same manner as the relationship between the first and second surface elements b, c, with this same relationship continuing along the length of the exterior surface of the inner sleeve piece.  
           [0010]    The second or outer sleeve piece  15 ′ of the two-piece sleeve is designed as a reverse image of the first inner sleeve piece  15   a . Thus, the outer second sleeve piece  15 ′ has a cylindrical outer peripheral surface and an inner surface provided with saw-tooth-shaped surface elements that are complementary to those of the first sleeve piece  15   a . The outer second sleeve piece  15 ′ is arranged to enclose the inner sleeve piece  15   a , with a short section f of the inner sleeve  15   a  projecting axially beyond the interior of the outer second sleeve piece  15 ′ as shown in FIG. 1.  
           [0011]    This known attachment mechanism also incorporates a ring member  16  arranged around the shaft  10  on the side of the machine member  11  facing away from the shoulder  12 . This ring member  16  is provided with a number of axially extending through-holes  16   a , each of which receives a bolt  17  projecting through the through-hole  16   a  and screwed into a corresponding one of several threaded bores  18  in the machine member  11 . This ring member  16  abuts the projecting sleeve portion f of the inner sleeve  15   a . By tightening the bolts  17 , it is possible to axially move the inner sleeve piece  15   a  relative to the outer sleeve piece  15 ′ to cause the cooperating tapering surfaces of the inner and outer sleeve pieces  15   a ,  15 ′ to slide against each other, thereby first reaching the radial measure x of the space  13 , and thereafter upon continued tightening of the bolts increasing the grip between the attachment mechanism and the shaft  10  as well as between the attachment mechanism and the interior of the machine member  11  until a firm grip is obtained in the circumferential as well as in the axial direction.  
           [0012]    By virtue of the consecutive saw-tooth-shaped taper portions being made in an integral unit, the attachment mechanism is centered in its seat without risk of misalignment. In addition, the handling and stock-keeping of the attachment mechanism is somewhat simplified.  
           [0013]    The known attachment mechanism described above and illustrated in FIG. 1 provides very good and reliable attachment results. However, the arresting of sheaves of various bore diameters requires stock-keeping a large variety of sizes of the attachment mechanisms. Alternatively, this requires separate manufacture for different relationships between the bore and shaft diameter.  
           [0014]    A need thus exists for an improved attachment mechanism of the type mentioned above which is not as susceptible to the drawbacks mentioned above, and which is useful for a wide variety of sheave bore diameters with only a few different sizes.  
         SUMMARY OF THE INVENTION  
         [0015]    One aspect of the invention involves an attachment device mounted with respect to a machine member and a cylindrical shaft to arrest the machine member on the shaft, wherein the machine member has a tapering bore of greater diameter than the outer diameter of the shaft so that an annular space exists between the machine member and the shaft. The attachment device includes a two-part sleeve positioned in the annular space to provide a clamping force between the shaft and the machine member, with the two-part sleeve comprising first and second sleeve parts. Each of the first and second sleeve parts has mating, cooperating taper surfaces facing each other so that upon mutual displacement the first and second sleeve parts change their overall radial size. A first ring member is arranged about the shaft and forms a stop for the first sleeve part. At least one bolt is positioned in a hole in the first ring member and in a bore in the machine member to move the machine member relative to the shaft and effect the mutual displacement of the first and second sleeve parts. A second ring member is positioned between the two-part sleeve and the machine member, and has a tapered outer surface that matches the taper of the bore in the machine member. The second ring member has an inwardly projecting flange located at the axial end of the second ring member which faces away from the first ring member, with the inwardly projecting flange forming an abutment for the second sleeve part to transfer axial displacement of the machine member into the mutual displacement of the first and second sleeve parts.  
           [0016]    Another aspect involves an attachment unit adapted to be mounted about a cylindrical shaft to arrest a machine member, provided with a tapered bore of greater diameter than a diameter of the cylindrical shaft so that an annular space exists between the shaft and the machine member, on the cylindrical shaft. The attachment unit includes a two-part sleeve adapted to be positioned in the annular space to provide a clamping force between the shaft and the machine member, with the two-part sleeve comprising an inner sleeve part and an outer sleeve part encircling the inner sleeve part. The inner sleeve part and the outer sleeve part each have a first end and a second end, with the second end of the outer sleeve part extending axially beyond the second end of the inner sleeve part. The inner sleeve part has a cylindrical inner surface and an outer surface provided with a plurality of axially arranged taper surfaces, and the outer sleeve part has a cylindrical outer surface and an inner surface provided with a plurality of axially arranged taper surfaces. The taper surfaces on the inner sleeve part face the taper surfaces on the outer sleeve part to cooperate with each other so that mutual displacement of the inner and outer sleeve parts effects a change in overall radial size of the inner and outer sleeve parts. A first ring member is positioned adjacent the first end of the inner sleeve part and forms a stop for engaging the first end of the inner sleeve part. A supporting device is adapted to axially move the machine member with respect to the shaft to effect the mutual displacement of the inner and outer sleeve parts. A second ring member has an inner surface facing the outer surface of the outer sleeve part, and is provided with a tapering outer surface and an inwardly projecting flange located adjacent the second end of the outer sleeve part to form an abutment for the second end of the outer sleeve part to transfer an axial displacement of the machine member into the mutual displacement of the inner and outer sleeve parts.  
           [0017]    The attachment device or unit is quite advantageous in that it is useful for a wide variety of sheave bore diameters with only a few different sizes.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES  
       [0018]    The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawing figures in which like reference numerals designate like elements.  
         [0019]    [0019]FIG. 1 is a cross-sectional view of a machine member arrested to a shaft by way of a known attachment mechanism.  
         [0020]    [0020]FIG. 2 is a cross-sectional view of a portion of a sheave attached to a shaft by way of an attachment device or attachment mechanism in accordance with the present invention.  
         [0021]    [0021]FIG. 3 is a cross-sectional view similar to FIG. 2, but illustrating a second embodiment of the attachment device according to the present invention.  
         [0022]    [0022]FIG. 4 is a cross-sectional view corresponding to FIG. 3 and showing an attachment device of a somewhat more compact design. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    [0023]FIG. 2 illustrates in cross-section a first embodiment of an attachment device or attachment unit according to the present invention. The attachment device includes a shaft  20 , a machine member which in the illustrated embodiment is in the form of a sheave  21  (only a portion of which is shown), a first ring member  26  arranged around or encircling the shaft  20 , and a plurality of supporting devices or bolts  27 . Each of the bolts  27  extends through a bore or hole in the first ring member  26  and is screwed into a threaded bore or hole  28  in the machine member or sheave  21 .  
         [0024]    A two-part thin-walled sleeve  25  is positioned around and encircles the shaft  20 . This two-part sleeve  25  is of the same construction as the two-part sleeve described above in connection with the illustration in FIG. 1. The two-part sleeve  25  comprises a first sleeve part  25   a  constituting an inner sleeve and a second sleeve part  25   b  constituting an outer sleeve part. The first sleeve part  25   a  has a cylindrical inner surface and an external surface provided with an axially arranged series of tapering substantially saw-tooth-shaped surface elements. The second sleeve part  25   b  has a cylindrical outer peripheral surface and an inner surface provided with an axially arranged series of tapering saw-tooth-shaped surface elements that are complementary to those of the first sleeve part  25   a . The second sleeve part  25   b  encloses or surrounds the first sleeve part  25   b , with a short section of the inner sleeve part  25   a  at the end closest to the first ring member  26  projecting axially beyond the second sleeve part  25   b  as shown in FIG. 2. The first ring member  26  is arranged about the shaft  20  and forms a stop for the axial end of the inner sleeve part  25   a.    
         [0025]    The attachment mechanism used in FIG. 2 differs from that associated with the known version shown in FIG. 1 in that the bore  24  of the machine member  21  is tapered, rather than being cylindrical. In addition, an intermediately located second ring member  29  having an external tapering peripheral surface portion  30  is provided with a cylindrical inner surface  21   a . This inner surface  21   a  of the second ring member  29 , together with the outer peripheral surface of the shaft  20 , defines a space in which the two-part sleeve member  25  is positioned.  
         [0026]    One of the axial ends of the second ring member  29  has an inwardly projecting flange  22  forming an abutment for the outer sleeve part  25   b . In the illustrated embodiment, the inwardly projecting flange  22  is located at the end of the second intermediately located ring member  29  that is remote from the first ring member  26 . This inwardly projecting flange  22  has an inner diameter substantially corresponding to that of the shaft  20  to allow the second ring member  29  to be easily positioned around the shaft  20 .  
         [0027]    In this embodiment, one axial end of the second ring member  29  is provided with a radially outwardly projecting flange member  31 . In this embodiment, the radially outwardly projecting flange member  31  is located at the axial end of the of the second ring member  29  located closer to the ring member  26 . Thus, the inwardly projecting flange  22  and the outwardly projecting flange  31  are located at opposite axial ends of the second ring member  29 . The outwardly projecting flange member  31  is provided with axially extending bores  32  aligned with or arranged to correspond in position to the bores in the first ring member  26  and the bores  28  in the machine member  21 . Also, the flange  31  (i.e., the intermediate ring member  29 ) is relatively easily rotated in order to align the through bores  32  with the through bores in the first ring member  26  and in the machine member  21 .  
         [0028]    The operation and effect of the two-part sleeve member  25  shown in FIG. 2 is the same as that of the sleeve member  15  shown in FIG. 1 and described above. Thus, when the second intermediately located ring member  29  is applied with a substantially axial force to the left in FIG. 2, the second sleeve part  25   b  of the two-part sleeve  25  will be pushed to the left through contact with the adjacent shoulder formed by the inwardly extending flange  22  on the second ring member  29 . However, the first sleeve part  25   a  of the two-part sleeve  25  will abut against the first ring member  26  and so the outer sleeve member will move up over the first sleeve part  25   a , thus increasing the total radial size of the pair of sleeve members while also increasing the grip of the two-part sleeve  25  against the shaft  20  and against the second ring member  29 . As a result, the force arresting the second ring member  29  on the shaft  20  is also increased.  
         [0029]    [0029]FIGS. 3 and 4 are cross-sectional views corresponding to the FIG. 2 illustration, but depicting attachment devices according to further embodiments of the present invention that are slightly different from the attachment device shown in FIG. 2. Components of these alternative embodiments that are the same as in the embodiment shown in FIG. 2 are designated by like reference numerals.  
         [0030]    [0030]FIG. 3 illustrates a shaft  20  to which is attached an annular machine member  21  which in the illustrated version is in the form of a sheave. A two-part thin-walled sleeve  25  and a first ring member  26  are arranged about and encircle the shaft  20 . The two-part sleeve is comprised of the inner sleeve part or first sleeve part  25   a  and the outer sleeve part or second sleeve part  25   b . A plurality of bolts  27  extend through respective bores in the first ring member  26  and are threadably connected with corresponding threaded bores  28  in the machine member or sheave  21 . The machine member  21  possesses a tapering bore  24 . Positioned between the two-part sleeve  25  and the bore  24  of the machine member  21  is an intermediately located ring  39  which has a tapering outer peripheral surface  40  corresponding to the tapering bore  24  of the machine member  21 . This intermediately located ring  39  has an inwardly projecting flange  42  closely encircling the periphery of the shaft  20 , and thereby also forming an annular shoulder acting on the outer sleeve part  25   b  of the two-part sleeve  25  upon application of an axial force in the same manner as described above.  
         [0031]    This second embodiment differs from the first embodiment shown in FIG. 2 insofar as the configuration of the intermediately located ring. In this second embodiment, the intermediately located ring  39  has no outwardly extending flange corresponding to the flange  31  in the first embodiment shown in FIG. 2. Rather, in the second embodiment shown in FIG. 3, the bolts  27  extend directly from the bores in the first ring member  26  and enter into the threaded bores  28  in the machine member or sheave  21 . The functioning, effect and operation of the attachment device illustrated in FIG. 3 is are similar to those in the embodiment according to FIG. 2.  
         [0032]    Referring to FIG. 4, a third embodiment of the present invention is illustrated which is similar to the embodiment shown in FIG. 3, except that the two-part thin-walled sleeve  25 ′, comprised of the inner sleeve part or first sleeve part  25   a ′ and the outer sleeve part or second sleeve part  25   b ′, possesses a substantially shorter axial dimension than the corresponding dimension of the two-part sleeve shown in FIG. 3. Therefore, with this construction, it is also possible to use an intermediately located ring  39 ′ that is of substantially sorter axial dimension. This shorter construction of the attachment device can preferably be used when the forces to be transferred between the shaft and the machine element (e.g., sheave) are relatively small.  
         [0033]    In the embodiments according to FIGS. 3 and 4, the bolts  27  have no intermediate guidance via bores in a flange extending outwardly from the intermediary ring  39 ,  39 ′. For most applications, such intermediate guidance is not necessary.  
         [0034]    The components forming part of the attachment device according to the invention can be temporarily interconnected and held together as a unit after manufacture and can be delivered to the place of use as a single unit. Upon assembly, the unit can be pushed up on the shaft to the desired position, whereupon the bolts are tightened until the grip between the different cooperating surfaces is as desired. A further advantage of this construction is that bolts and tapering portions of a standard type can be used.  
         [0035]    It is to be understood that although the embodiments described above and illustrated in the drawing figures depict the machine member in the form of a sheave, the invention has application to other types of machine members. For example, the machine member can be in the form of a pulley, a sprocket or the like.  
         [0036]    The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing specification. However, the invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. Further, the embodiments described herein are to be regarded as illustrative rather than restrictive. Variations and changes may be made by others, and equivalents employed, without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such variations, changes and equivalents which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby.

Technology Category: 4