Abstract:
A mounting device for coaxially anchoring a machine element upon a rotary shaft is provided. The device fits between the interior bore of the machine element and the cylindrical surface of the shaft and is effective to position the element at any desired position longitudinally of the shaft and at any angular position circumferentially of the shaft. The device has inner and outer sleeves, the mating surfaces of which are similarly tapered so that relative axial displacement of the sleeves affects expansion and contraction of the interior bore and external surface of the combined elements. Rotation of a threaded nut at one end of the device effects the relative axial displacement of the inner and outer sleeves to afford expansion and contraction of the sleeves without excessively straining the material of the sleeves or the nut.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Application No. 61/734,318 filed Dec. 6, 2012. The entire disclosure of the foregoing application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a mounting device for mounting a machine element on a shaft. The device provides an improved mounting device for mounting machine elements permitting infinitely-variable adjustment of the machine element on the shaft, both axially of the shaft and circumferentially, while maintaining the machine element at a fixed, axial position after being mounting on the shaft. 
       BACKGROUND OF THE INVENTION 
       [0003]    The use of devices for mounting machine elements, such as pulleys and gears, upon a shaft is well-known. One difficulty is that the known devices for mounting a machine element upon a cylindrical shaft are cumbersome to use. For example, some devices require assembly of multiple pieces and adjustment of several screws, and other devices require modification of the shaft on which the machine element is mounted. 
         [0004]    Another difficulty frequently encountered relates to the need for precise positioning of the machine elements circumferentially on the shaft when the machine element is mounted upon the shaft. Specifically, it is desirable to position the machine element at a particular circumferential position and maintain the element at such position after the element is attached to the shaft. In addition, it is desirable to allow for the infinitely-variable adjustment of the machine element prior to attaching the element to the shaft. One known device is disclosed in U.S. Pat. No. 5,695,297. Although such devices have overcome issues of previous devices, issues remain with providing an easily installed mounting device in certain applications. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with the present invention, a mounting device is provided that is easy to use. The device enables the mounting of a machine element by simply tightening a single nut to effect frictional engagement and also to ensure disengagement by loosening the same nut. The nut operates to positively release the frictional engagement produced by tightening the nut. 
         [0006]    The present invention also solves the difficulty of maintaining the machine element at a fixed position. Once mounted, the device retains the machine element at a fixed, axial position relative to the shaft. 
         [0007]    The present invention provides a device for coaxially mounting a machine element having a bore upon a shaft. The mounting device includes an outer sleeve for engaging the machine element and an inner sleeve for engaging the shaft. The inner and outer sleeves have cooperating tapered surfaces so that displacing the inner sleeve relative to the outer sleeve creates radial forces that lock the outer sleeve against the bore of the machine element and the inner sleeve against the shaft. A nut connected with at least one of the inner and outer sleeve is operable to displace the inner sleeve relative to the outer sleeve. 
         [0008]    According to one aspect, the present invention provides a device for coaxially mounting a machine element having a bore upon a shaft. The device includes a nut, an inner sleeve and an outer sleeve. The nut includes an enlarged head, a first connector and a threaded portion overlying at least a portion of the first connector. The outer sleeve engages the machine element and it includes an external surface configured to cooperate with the bore of the machine element, a tapered internal surface and at least one axial slot extending longitudinally along the outer sleeve to permit expansion of the external surface of the outer sleeve. The outer sleeve also includes an internally threaded portion configured to threadedly engage the threads of the nut. The inner sleeve encircles the shaft and it includes a tapered external surface corresponding in angle of taper to the tapered internal surface of the outer sleeve, an interior bore corresponding in diameter to the shaft, and a second connector cooperable with the first connector to connect the inner sleeve with the nut. The connection between the nut and the inner sleeve impedes substantial axial displacement of the inner sleeve relative to the nut while allowing rotation of the outer sleeve relative to the inner sleeve. The enlarged head of the nut is larger than the outer sleeve so that the enlarged head can abut a sidewall of the machine element when the machine element is mounted on the device. Rotating the nut in a first direction displaces the outer sleeve rearwardly relative to the nut, which displaces the major diameter of the external surface of the inner sleeve toward the minor diameter of the outer sleeve internal surface, thereby causing the inner sleeve to contract against the shaft and the outer sleeve to expand against the bore of the machine element. Rotating the nut in a second direction displaces the outer sleeve forwardly relative to the nut, thereby loosening the inner sleeve from the shaft and the outer sleeve from the bore of the machine element. 
         [0009]    According to a second aspect, the present invention provides a device for coaxially mounting a machine element having a bore upon a shaft. The device includes a one-piece inner sleeve for encircling the shaft and having a frustoconical external surface, an interlock at a first end, and a circumferential or annular recess at a second end remote from the interlock. The inner sleeve is connected with a nut having a threaded portion and a second interlock configured to cooperate with the first interlock to substantially permanently connect the inner sleeve with the nut to allow rotation of the inner sleeve relative to the nut while substantially impeding axial movement of the inner sleeve relative to the nut. The nut further includes an enlarged head. The device also includes an outer sleeve for engaging the machine element. The outer sleeve includes a threaded portion configured to threadedly engage the nut, a frustoconical internal surface corresponding in angle of taper to the tapered external surface of the inner sleeve and an external surface corresponding to the bore of the machine element. The device may also include a spacer sleeve having an internal surface correlating with an outer surface of the outer sleeve so that the spacer sleeve fits over the outer sleeve to position the device relative to the machine element. 
         [0010]    Accordingly to yet another aspect, the present invention provides a method for mounting a machine element onto a shaft. According to the method, an inner sleeve is provided, which has a tapered external surface and a bore that is cooperable with the shaft. An outer sleeve is provided, which has an internal bore that is tapered to cooperate with the external surface of the inner sleeve, a threaded portion, and an external surface cooperable with the bore of the machine element. A nut is provided, which has an enlarged head and a threaded portion that is cooperable with the threaded portion of the outer sleeve. The inner sleeve is connected to the nut to impede substantial axial displacement of the inner sleeve relative to the nut while allowing rotation of the nut relative to the inner sleeve. A positioning sleeve is positioned over a portion of the outer sleeve. The inner and outer sleeves are positioned between the shaft and the bore of the machine element so that a rearward edge of the positioning sleeve abuts the enlarged head of the nut and a forward edge of the positioning sleeve abuts a sidewall of the machine element without extending into the bore of the machine element. The nut is rotated in a forward direction to drive the outer sleeve axially relative to the nut and the inner sleeve so that the tapered surface of the inner sleeve wedges apart the outer sleeve to connect the outer sleeve to the machine element and the inner sleeve to the shaft. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The foregoing summary, as well as the following detailed description of the preferred embodiments of the present invention, will be better understood when read in conjunction with the appended drawings, in which: 
           [0012]      FIG. 1  is an enlarged sectional view of a mounting device illustrated in combination with a machine element and a shaft. 
           [0013]      FIG. 2  is an exploded perspective view of the mounting device illustrated in  FIG. 1 . 
           [0014]      FIG. 3  is a perspective broken away view of the mounting device illustrated in  FIG. 1 . 
           [0015]      FIG. 4  is an end view of the mounting device illustrated in  FIG. 1 . 
           [0016]      FIG. 5  is a sectional view of the mounting device illustrated in  FIG. 4  taken along the line  5 - 5 . 
           [0017]      FIG. 6  is an enlarged sectional view of an alternate mounting device illustrated in combination with a machine element and a shaft. 
           [0018]      FIG. 7  is an exploded perspective view of the mounting device illustrated in  FIG. 6 . 
           [0019]      FIG. 8  is a perspective broken away view of the mounting device illustrated in  FIG. 6 . 
           [0020]      FIG. 9  is an end view of the mounting device illustrated in  FIG. 6 . 
           [0021]      FIG. 10  is a sectional view of the mounting device illustrated in  FIG. 9  taken along the line  10 - 10 . 
           [0022]      FIG. 11  is an exploded perspective view of a second alternate mounting device. 
           [0023]      FIG. 12  is a perspective broken away view of the mounting device illustrated in  FIG. 11 . 
           [0024]      FIG. 13  is an end view of the mounting device illustrated in  FIG. 11 . 
           [0025]      FIG. 14  is a sectional view of the mounting device illustrated in  FIG. 13  taken along the line  14 - 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0026]    Referring now to the drawings and to  FIGS. 1-5  specifically, a mounting device is designated generally  10 . The mounting device is designed to mount a first element, such as a machine element  12 , onto a second element, such as a shaft  15 . The machine element  12  has a bore that engages the external surface of the mounting device  10 , and the shaft  15  has a surface that engages the internal surface of the mounting device  10 . In the present instance, the machine element  12  has a smooth tapered bore  13  whose axis coincides with the axis of the cylindrical surface of the shaft  15 . The mounting device is designed to be positioned between the machine element  12  and the shaft  15  and to be expanded to securely anchor the machine element  12  onto the shaft at a desired position axially of the shaft and an angular position circumferentially of the shaft. 
         [0027]    The mounting device  10  includes an inner sleeve  20 , an outer sleeve  50 , and a locking nut  40 . The external surface  23  of the inner sleeve  20  is formed to cooperate with the inner surface of the outer sleeve as discussed further below. Specifically, the forward end of the inner sleeve has a frustoconical tapered external surface  23 . The frustoconical surface  23  is configured so that the minor diameter is adjacent the forward edge of the inner sleeve and the major diameter is spaced rearwardly from the forward edge. In other words, the largest diameter of the frustoconical surface  23  is located intermediate the ends of the inner sleeve and the surface tapers inwardly as the surface extends toward the forward end of the inner sleeve. The external surface of the sleeve also includes an interlock for connecting the inner sleeve with the locking nut  40 . 
         [0028]    In the present instance, the interlock of the inner sleeve is configured to connect the inner sleeve to the nut so as to allow the inner sleeve to rotate relative to the nut while substantially impeding axial movement of the inner sleeve relative to the nut. For example, the interlock may comprise a circumferential flange  24  that extends around the circumference of the inner sleeve  20 , projecting radially outwardly. Further, the interlock may comprise a circumferential groove  26  that extends around the circumference of the inner sleeve adjacent the circumferential flange  24 . 
         [0029]    The inner sleeve  20  is tubular in form having an internal bore that cooperates with the external surface of the shaft  15 . Specifically, if the external surface of the shaft is tapered or frustoconical, the internal surface of the inner sleeve has a cooperating tapered or frustoconical surface. In the present instance, the shaft is cylindrical, and the inner sleeve  20  has a cylindrical bore with a diameter that corresponds to the diameter of the shaft  15 . Preferably, the bore of the inner sleeve is slightly greater in diameter than the shaft  15  to permit free sliding movement of the inner sleeve  20  on the shaft  15  both axially and circumferentially. 
         [0030]    As discussed further below, the inner sleeve engages the shaft  15  by contracting so that the inner sleeve grips or clamps down onto the shaft. For this purpose, the inner sleeve  20  is formed into a plurality of segments by slots  22  that extend longitudinally through the sleeve from the forward end. The slots  22  allow radial deflection of the inner sleeve as the mounting device is tightened or released. The slots terminate along a line spaced inwardly from the forward end of the inner sleeve  20 . In this way, the forward portion of the inner sleeve  20  may form an unsplit solid continuous ring portion. However, in the present instance, the inner sleeve is made from steel and provided with six equally spaced slots, one of which extends through the entire length of the inner sleeve. It will be recognized, however, that the number of slots, as well as the width, length and spacing of the slots can be varied to achieve the desired flexibility. 
         [0031]    The inner sleeve  20  is adapted to fit within the outer sleeve  50 , which is a unitary sleeve having a plurality of axial slots  52  extending from the rearward end of the outer sleeve. The axial slots  52  permit radial deflection of the outer sleeve  50  as the mounting device  10  is tightened and released. The outer surface of the outer sleeve  50  has an engaging surface  53  that is configured to cooperate with the internal bore of the machine element  12 . For example, the machine element bore may be cylindrical and the engaging surface  53  of the outer sleeve may correspondingly be generally cylindrical. Alternatively, the engaging surface  53  of the outer sleeve may be frustoconical to cooperate with a machine element having a tapered bore. In addition, preferably the engaging surface  53  is sufficiently smaller than the bore of the machine element to permit free sliding movement between the machine element and the outer sleeve when the mounting device is not tightened. 
         [0032]    As shown in  FIG. 1-5 , the inner surface of the outer sleeve  50  is configured to cooperate with the external surface  23  of the inner sleeve. The inner and outer sleeves have mating tapered surfaces that cooperate to wedge the outer sleeve outwardly while contracting the inner sleeve inwardly. More specifically, the inner surface of the outer sleeve  50  tapers toward the forward end at the same angle of taper as the frustoconical portion  23  of the inner sleeve  20 . In other words, the bore of the outer sleeve is tapered so that the minor diameter of the bore is adjacent the forward end of the outer sleeve and the major diameter of the bore is spaced rearwardly from the forward end. In this way, when the outer sleeve  50  is displaced rearwardly relative to the inner sleeve  20  (i.e. from right to left in  FIG. 1 ), the confronting tapered surfaces of the inner and outer sleeves cooperate to expand the external cylindrical surface of the outer sleeve and contract the internal cylindrical surface of the inner sleeve. 
         [0033]    In the present instance, the outer sleeve comprises a threaded portion  55  configured to threadedly engage the threaded portion  42  of the lock nut  40 . Specifically, the outer sleeve comprises an internally threaded section  55  adjacent the rearward end of the outer sleeve. To affect this displacement, as illustrated in  FIGS. 1-5 , the nut  40  has external threads  42  that threadedly engage the threads  55  of the outer sleeve  50 . Rotating the nut  40  displaces the outer sleeve axially relative to the nut. Accordingly, since the inner sleeve  20  is connected to the nut, the outer sleeve is displaced relative to the inner sleeve as the nut is rotated. 
         [0034]    The nut  40  has an internal bore that is larger than the diameter of the shaft  15 . In addition, preferably the outer diameter of the nut is larger than the outer diameter of the outer sleeve  50 . More specifically, the nut  40  has an enlarged head  44  that extends radially outwardly so that the diameter of the head is larger than the bore of the machine element. Therefore, the outer diameter of the head  44  is larger than the largest diameter of the outer sleeve  50 . In this way, the head  44  of the nut  40  is configured so that if the head of the nut is abutted against the machine element, the head operates as a stop to impede displacement of the machine element relative to the nut. Additionally, as discussed above, the nut is connected to the inner sleeve in a manner that substantially impedes axial displacement of the inner sleeve relative to the nut. Therefore when the head  44  of the nut  40  abuts the side of the machine element, the head operates as a stop impeding axial displacement of the machine element relative to the inner sleeve. The mating tapers of the inner and outer sleeve are configured so that displacement of the outer sleeve relative to the inner sleeve imparts greater radial force than axial force. Therefore, the forces created by the cooperating tapers cause greater clamping force than axial forces. Because of this, tightening the locking nut causes the inner sleeve to clamp down on the shaft  15  with sufficient force to impede axial displacement of the inner sleeve relative to the shaft in response to the axial forces caused by the mating tapers when the inner and out sleeves are displaced relative to one another to tighten the device. 
         [0035]    As discussed above, the nut  40  is connected to the inner sleeve  20  to impede substantial axial displacement between the nut and the inner sleeve. To provide such a connection, the nut  40  comprises an interlock configured to cooperate with the interlock of the inner sleeve  20  to provide a substantially irreversible or permanent connection that allows the inner sleeve to rotate relative to the nut while substantially impeding axial displacement of the inner sleeve relative to the nut. In the present instance, the nut comprises an annular flange  48  and an annular groove  46  configured to cooperate with the circumferential flange  24  and circumferential groove  26  of the inner sleeve  20 . Preferably, the forward and rearward sidewalls of the groove  46  are substantially perpendicular to the common axis of the assembly. In the present instance, the groove  46  and flange  48  are formed inside the nut  40  at the forward end of the nut. In this way, the threaded portion  42  of the nut overlies groove  46  and flange  48  as shown in  FIGS. 1 and 5 . In this way, the interlock between the nut and the inner sleeve is coextensive with at least a portion of the threaded portion  42  of the nut. More particularly, in the present instance, the entire axial length of the interlocking surfaces between the inner sleeve and the nut are coextensive with at least a portion of the threaded section  42  of the nut  40 . 
         [0036]    The interlock between the inner sleeve  20  and the nut  40  operates as follows. The external flange  24  of the inner sleeve  20  engages the annular groove  46  of the nut  40 , and the internal flange  48  of the nut engages the circumferential groove  26  of the inner sleeve. Accordingly, the external flange  24  of the inner sleeve  20  has a width that is slightly less than the width of the internal groove  46  of the nut, and the internal flange  48  of the nut has a width that is slightly less than the width of the circumferential groove  26  of the inner sleeve. 
         [0037]    The inner diameter of the internal flange  48  of the nut is smaller than the outer diameter of the external flange  24  on the inner sleeve, and the external flange on the inner sleeve passes over the nut flange  48  to connect the inner sleeve to the nut. Therefore, to connect the one-piece inner sleeve  20  to the nut  40 , the inner sleeve has sufficient flexibility to allow the inner sleeve to radially contract sufficiently to fit through the reduced diameter formed by the flange  48  of the nut  40 . Accordingly, as discussed above, the inner sleeve  20  is formed into a plurality of segments by means of slots  22  that extend axially longitudinally of the sleeve from the rearward end. The slots form a flexible web  32  that is sufficiently flexible to allow the rearward end of the inner sleeve to resiliently deform radially to allow the interlock of the inner sleeve to connect with the interlock of the outer sleeve. 
         [0038]    In the present instance, the interlock of the inner sleeve is an external interlock and the nut comprises an internal interlock. Therefore, the web provides sufficient flexibility to allow the inner sleeve to deform radially inwardly sufficiently to allow the interlock of the inner sleeve to pass through a reduced diameter portion of the internal interlock of the nut. Alternatively, the nut may comprise an external interlock and the inner sleeve may comprise a corresponding internal interlock. In such an embodiment, the web  32  provides sufficient flexibility to allow the inner sleeve to resilient deform radially outwardly to expand sufficiently to allow the internal interlock of the inner sleeve to fit over the external interlock of the nut. Furthermore, the web  32  is sufficiently resilient such that after the inner sleeve contracts inwardly to fit through the reduced diameter of the internal interlock of the nut, the inner sleeve resiliently expands outwardly so that the flange  24  nests within the groove  46  inside the nut as shown in  FIGS. 1 and 5 . Similarly, if the nut comprises an external interlock, after the inner sleeve  20  expands radially outwardly sufficiently to fit over an enlarged diameter of the external interlock, the inner sleeve resiliently contracts radially inwardly so that the internal interlock of the inner sleeve engages the external interlock of the nut. 
         [0039]    Accordingly, the mounting device  10  is assembled as follows. Inner sleeve  20  is aligned with the nut so that the central axis of the nut is aligned with the central axis of the inner sleeve. In this way, the interlock of the nut is aligned with the interlock of the inner sleeve. The inner sleeve  20  is then displaced axially relative to the nut to drive the inner sleeve toward the nut. Additionally, the rearward end of the inner sleeve  20  is compressed inwardly so that the interlock of the inner sleeve fits within the interlock of the nut. Specifically, the inner sleeve is deformed radially inwardly so that the outer diameter of the circumferential flange is smaller than the reduced diameter of the annular flange  48  of the nut. 
         [0040]    To effectuate contraction of the inner sleeve, the rearward face of the circumferential flange  24  is chamfered as shown in  FIGS. 1 and 2 . In this way, driving the inner sleeve  20  toward the nut  40  deforms the circumferential flange  24  radially inwardly as the chamfered edge engages the annular flange  48  of the nut. After the flange  24  passes through the reduced diameter bore of the internal flange  48 , the flange  24  resiliently expands outwardly so that the flange  24  engages the annular groove  46  in the nut and the internal flange  48  engages the circumferential flange  26  of the inner sleeve. 
         [0041]    The outer sleeve  50  is then threaded onto the nut  40  so that the outer sleeve overlies the inner sleeve  20  as shown in  FIG. 1 . In the present instance, the outer sleeve is threaded onto the nut a sufficient distance so that the mating frustoconical surfaces  24 ,  53  of the inner and outer sleeves do not sufficiently engage each other during assembly to cause the inner sleeve to deform radially inwardly. The assembled mounting device can then be placed onto a shaft  15  by sliding the shaft through the inner sleeve  20 . Similarly, a machine element may be mounted onto the device  10  by inserting the outer sleeve  50  into the bore of the machine element  12  to that the head  44  of the nut  40  abuts the hub or sidewall of the machine element. The machine element  12  is mounted onto the device so that the bore of the machine element overlies the mating tapered surfaces of the inner and outer sleeves. Specifically, in the present instance more than half the width of portion of the machine element that engages the mounting device overlies the mating tapered surfaces of the inner and outer sleeves rather than overlying the rearward portion of the inner and outer sleeves. 
         [0042]    To lock the machine element  12  onto the shaft  15 , the nut  40  is rotated. As can be seen in  FIG. 1 , the wedging action of the inner and outer sleeves is provided by displacing the inner sleeve forward relative to the outer sleeve. Specifically, when the device is in a loosened position, the inner sleeve is located within the outer sleeve so that the major diameter of the inner sleeve frustoconical portion  23  is positioned within a portion of the outer sleeve bore having a diameter that is at least as great as the major diameter of the inner sleeve frustoconical portion. In other words, in the loosened position, the inner sleeve  20  does not contact the bore of the outer sleeve to provide a wedging or clamping force. 
         [0043]    Rotating the nut  40  in a forward direction displaces the outer sleeve  50  rearwardly relative to the inner sleeve  20  so that the internal tapered surface of the outer sleeve is driven over the frustoconical surface  23  of the inner sleeve  20 . Driving the outer sleeve rearwardly wedges the outer sleeve so that the outer sleeve deflects radially outwardly to expand the outer sleeve in the bore of the machine element  12  to lock onto the machine element. At the same time, the wedging force deflects the inner sleeve radially inwardly so that the inner sleeve contracts to lock the inner sleeve  20  onto the shaft  15 . 
         [0044]    To release the connection between the machine element, mounting device and shaft, the nut is simply rotated in a reverse direction. The reverse rotation displaces the outer sleeve forwardly relative to the inner sleeve. The forward relative displacement of the outer sleeve drives the major diameter of the outer sleeve internal tapered portion over the larger diameter portion of the frustoconical portion  23  of the inner sleeve, which in turn releases the wedging force provided by the interfering tapered surfaces. In this way, rotating the nut in the reverse direction loosens the outer sleeve from the machine element and loosens the inner sleeve from the shaft. 
         [0045]    The angle of taper of the external surface of the inner sleeve  20  and the internal surface of the outer sleeve  50  is selected relative to the length of the threaded portion  52  of the outer sleeve. A shallower angle permits greater displacement of the outer sleeve  50  relative to the inner sleeve  20  with less expansion of the mounting device  10 . Alternatively, a sharper angle reduces the relative displacement of the sleeves before expansion of the device. 
         [0046]    As shown in  FIGS. 1-5 , the device  10  includes several optional features that can be incorporated into the device depending on the application. For instance, as shown in  FIGS. 1 ,  3  and  5 , the inner sleeve  20  may include a second circumferential groove or recess  34  at or adjacent to the forward end of the inner sleeve. Specifically, the second circumferential recess  34  is disposed adjacent an end opposite the end at which the interlock is formed. In the present instance, the recess  34  is formed in the web  32  of the inner sleeve. The recess  34  may be configured with sufficient depth and/or width to facilitate the web deforming elastically during the assembly process when the inner sleeve  20  is connected with the nut  40 . 
         [0047]      FIGS. 1-5  also illustrate an optional spacer sleeve, referred to as positioning sleeve  70 , disposed between the nut  40  and the outer sleeve  50 . The positioning sleeve  70  is a hollow substantially cylindrical ring having an internal surface sized and configured to cooperate with the external surface  53  of the outer sleeve  50 . Specifically, the inner surface  72  is a cylindrical surface having a diameter slightly larger than the outer diameter of the outer sleeve  50 . The positioning sleeve  70  may also comprise a retaining element to retain the positioning sleeve on the outer sleeve  50 . For instance, in the present instance, the positioning sleeve  70  comprises an annular flange  76  projecting radially inwardly to form a reduced diameter opening. In this way, the annular flange operates as a stop impeding the sleeve from sliding forwardly past the rearward edge of the outer sleeve  50  when the device is assembled, as shown in  FIGS. 1 and 5 . Additionally, in the present instance, the positioning sleeve is a substantially solid ring without slits or other features so that the positioning sleeve is substantially radially inflexible to impede the positioning sleeve from deforming radially outwardly in a manner that would allow the flange  76  to be displaced radially outwardly past the outer diameter of the outer sleeve  50 . 
         [0048]    The positioning sleeve  70  is configured with sufficient width to position the hub of the machine element over the tapered surfaces of the inner and outer sleeves  20 ,  50  when the machine element has a narrow width. Specifically, the forward edge  75  of the positioning sleeve (see  FIG. 5 ) extends outwardly from the head  44  of the nut so that the forward edge  75  engages the hub or sidewall of the machine element. In this way, the rearward end of the positioning sleeve abuts the head  44  of the nut  40  while the forward edge  75  engages the hub or sidewall of the machine element  12 . Additionally, the positioning sleeve  70  overlies at least a portion of the threaded portion  55  of the outer sleeve  50  and at least a portion of the externally threaded portion  42  of the nut  40 . 
         [0049]    When the positioning sleeve is incorporated into the device  10 , the device is assembled as follows. The inner sleeve  20  is connected to the nut  40  by driving the inner sleeve onto the nut as described above. The rearward end of the outer sleeve  50  is then inserted into the positioning sleeve. The inner sleeve/nut combination is then displaced axially relative to the outer sleeve/positioning sleeve combination until the internal threads of the outer sleeve engage the external threads of the nut. The device  10  is positioned onto a shaft  15  by inserting the shaft through the bore of the inner sleeve  20 . A machine element  12  is then mounted onto the device by inserting the device into the bore of the machine element until the forward edge  75  of the positioning sleeve engages the sidewall or hub of the machine element. In this way, the machine element is positioned over the tapered surfaces of the inner and outer sleeve rather than just the threaded portion of the outer sleeve. Additionally, since the positioning sleeve abuts the head  44  of the nut, the positioning sleeve and nut combine to impede relative displacement of the machine element relative to the nut and the attached inner sleeve when the nut is rotated to tighten the device. 
         [0050]    Referring now to  FIGS. 6-10 , an alternate embodiment of the mounting device described above is designated  110 . The mounting device comprises an inner sleeve  20  and a nut  40  configured substantially similar to the inner sleeve and nut  40  described above in connection with the mounting device  10 . The mounting further comprises an outer sleeve  150  and a positioning sleeve  170 . 
         [0051]    The inner surface of the outer sleeve  150  is configured to cooperate with the external surface  23  of the inner sleeve. The inner and outer sleeves have mating tapered surfaces that cooperate to wedge the outer sleeve outwardly while contracting the inner sleeve inwardly. More specifically, the inner surface of the outer sleeve  150  tapers toward the forward end at the same angle of taper as the frustoconical portion  23  of the inner sleeve  20 . When the outer sleeve  150  is displaced rearwardly relative to the inner sleeve  20  (i.e. from right to left in  FIG. 6 ), the confronting tapered surfaces of the inner and outer sleeves cooperate to expand the external cylindrical surface of the outer sleeve and contract the internal cylindrical surface of the inner sleeve. 
         [0052]    In the present instance, the outer sleeve  150  comprises a threaded portion  155  configured to threadedly engage the threaded portion  42  of the lock nut  40 . Specifically, the outer sleeve comprises an internally threaded section  155  adjacent the rearward end of the outer sleeve. To affect axial displacement of the outer sleeve relative to the inner sleeve, the nut  40  has external threads  42  that threadedly engage the threads  155  of the outer sleeve  150 . Rotating the nut  40  displaces the outer sleeve axially relative to the nut. Accordingly, since the inner sleeve  20  is connected to the nut, the outer sleeve is displaced axially relative to the inner sleeve as the nut is rotated. 
         [0053]    The outer sleeve  150  further comprises an external circumferential groove or recess  154  adjacent the rearward end of the outer sleeve. The positioning sleeve  170  is a substantially cylindrical ring having an internal surface configured to cooperate with the external surface of the outer ring  150 . Specifically, in the present instance, the internal surface  172  of the positioning ring is a cylindrical surface having a diameter substantially similar to the reduced diameter section formed by the recess  154  on the outer sleeve  150 . In this way, when the device is assembled, the positioning sleeve  170  is retained on the device  110  between the head of the nut  40  and the forward edge of the recess  154  formed on the outer surface of the outer sleeve. The assembly and operation of the mounting device  110  are substantially similar to the assembly and operation of the mounting device  10  described above. 
         [0054]    Referring now to  FIGS. 11-14  a second alternate embodiment of a mounting device is designated  210 . The mounting device  210  comprises a locking nut  240 , an inner sleeve  220 , and outer sleeve  50  and a positioning ring  270 . The outer sleeve  50  is substantially similar to the outer sleeve described above in connection with the first mounting device  10  described above. In this third embodiment, the interlock between the inner sleeve  220  and the nut  240  are reversed relative to the embodiments previously described. 
         [0055]    In the present instance, the interlock of the inner sleeve  220  is configured to connect the inner sleeve to the nut  240  so as to allow the inner sleeve to rotate relative to the nut while substantially impeding axial movement of the inner sleeve relative to the nut. For example, the interlock comprises an annular flange  224  that extends around the internal diameter of the inner sleeve  220 , projecting radially inwardly. Further, the interlock may comprise an annular groove  226  that extends around the internal diameter of the inner sleeve adjacent the annular flange  224 . 
         [0056]    The inner sleeve  220  is tubular in form having an internal bore that cooperates with the external surface of the shaft  15 . Specifically, if the external surface of the shaft is tapered or frustoconical, the internal surface of the inner sleeve has a cooperating tapered or frustoconical surface. In the present instance, the shaft is cylindrical, and the inner sleeve  220  has a cylindrical bore with a diameter that corresponds to the diameter of the shaft  15 . Preferably, the bore of the inner sleeve is slightly greater in diameter than the shaft  15  to permit free sliding movement of the inner sleeve  220  on the shaft  15  both axially and circumferentially. 
         [0057]    As discussed further below, the inner sleeve  220  engages the shaft  15  by contracting so that the inner sleeve grips or clamps down onto the shaft. For this purpose, the inner sleeve  220  is formed into a plurality of segments by slots  222  that extend longitudinally through the sleeve from the forward end. The slots  222  allow radial deflection of the inner sleeve as the mounting device is tightened or released. Preferably, the slots terminate along a line spaced inwardly from the forward end of the inner sleeve  220 . In this way, the forward portion of the inner sleeve  220  provides a flexible web that allows the inner sleeve to resiliently deform to interlock with the nut as discussed above in connection with the inner ring  20  of the first mounting device. 
         [0058]    The inner sleeve  220  is adapted to fit within the outer sleeve  50 . As shown in  FIG. 11-14 , the inner surface of the outer sleeve  50  is configured to cooperate with the external surface of the inner sleeve. The inner and outer sleeves have mating tapered surfaces that cooperate to wedge the outer sleeve outwardly while contracting the inner sleeve inwardly. More specifically, the inner surface of the outer sleeve  50  tapers toward the forward end at the same angle of taper as the frustoconical portion of the inner sleeve  220 . When the outer sleeve  50  is displaced rearwardly relative to the inner sleeve  220  (i.e. from right to left in  FIG. 11 ), the confronting tapered surfaces of the inner and outer sleeves cooperate to expand the external cylindrical surface of the outer sleeve and contract the internal cylindrical surface of the inner sleeve. 
         [0059]    In the present instance, the outer sleeve comprises a threaded portion  55  configured to threadedly engage the threaded portion  242  of the lock nut  40 . Specifically, the outer sleeve comprises an internally threaded section  55  adjacent the rearward end of the outer sleeve. To affect this displacement, as illustrated in  FIGS. 1-5 , the nut  240  has external threads  242  that threadedly engage the threads  55  of the outer sleeve  50 . Rotating the nut  240  displaces the outer sleeve axially relative to the nut. Accordingly, since the inner sleeve  220  is connected to the nut, the outer sleeve is displaced relative to the inner sleeve as the nut is rotated. 
         [0060]    The nut  240  has an internal bore that is larger than the diameter of the shaft  15 . In addition, preferably the outer diameter of the nut is larger than the outer diameter of the outer sleeve  50 . More specifically, the nut  240  has an enlarged head  244  that extends radially outwardly so that the diameter of the head is larger than the bore of the machine element. Therefore, the outer diameter of the head  244  is larger than the largest diameter of the outer sleeve  50 . In this way, the head  244  of the nut  40  is configured so that if the head of the nut is abutted against the machine element, the head operates as a stop to impede displacement of the machine element relative to the nut. Additionally, as discussed above, the nut is connected to the inner sleeve in a manner that substantially impedes axial displacement of the inner sleeve relative to the nut. Therefore when the head  244  of the nut  240  abuts the side of the machine element, the head operates as a stop impeding axial displacement of the machine element relative to the inner sleeve. The mating tapers of the inner and outer sleeve are configured so that displacement of the outer sleeve relative to the inner sleeve imparts greater radial force than axial force. Therefore, the forces created by the cooperating tapers cause greater clamping force than axial forces. Because of this, tightening the locking nut causes the inner sleeve to clamp down on the shaft  15  with sufficient force to impede displacement of the inner sleeve relative to the shaft from the axial forces caused by the mating tapers with the inner and out sleeves are displaced relative to one another to tighten the device. 
         [0061]    As discussed above, the nut  240  is connected to the inner sleeve  220  to impede substantial axial displacement between the nut and the inner sleeve. To provide such a connection, the nut comprises an interlock configured to cooperate with the interlock of the inner sleeve to provide a substantially irreversible or permanent connection that allows the inner sleeve to rotate relative to the nut while substantially impeding axial displacement of the inner sleeve relative to the nut. In the present instance, the nut comprises a circumferential flange  248  and a circumferential groove  246  configured to cooperate with the annular flange  224  and annular groove  226  of the inner sleeve  220 . In the present instance, the groove  246  and flange  248  are formed at the forward end of the nut, forward of the threaded portion  242 . 
         [0062]    Configured in this way, during assembly, the inner sleeve  220  expands radially outwardly over the circumferential flange  248  of the nut as the inner sleeve is driven toward the nut. The inner sleeve then resiliently contracts to lock the inner sleeve onto the forward end of the nut  240 . 
         [0063]    As shown in  FIG. 14 , the device  210  may also include a positioning ring  270 . The positioning sleeve  270  is a substantially cylindrical ring having an internal surface configured to cooperate with the external surface of the outer ring  50 . Specifically, in the present instance, the internal surface  172  of the positioning ring is a cylindrical surface having a diameter substantially similar to the diameter of the external cylindrical surface of the outer sleeve  50 . It should be noted that the positioning sleeve is retained between the head  244  of the nut  240  and the sidewall of the machine element  12 . However, when the machine element is separate from the mounting device, the positioning ring may slide over the outer sleeve. 
         [0064]    The assembly and operation of the mounting device  210  are substantially similar to the assembly and operation of the mounting device  10  described above. 
         [0065]    The mounting devices described above are particularly effective to avoid damage to the shaft and the machine elements in case of catastrophic overload of the machine. A major advantage of the construction of the mounting devices is that they slip and protect other elements of the machine without damage to the shaft or the machine element. In the event of slippage due to excess loading, the unit itself may not be damaged and may be used without replacement or readjustment. The construction also enables the units to be fabricated from materials other than metal where the operating conditions are such as to limit the selection of the material used in fabricating the parts. 
         [0066]    The use of a single-piece inner sleeve in conjunction with a single piece outer sleeve is particularly suited for situation in which precise rotary balance is required. In known devices incorporating a multiple piece inner or outer sleeve, the pieces comprising the multiple piece sleeve can move relative to one another when the device is tightened or loosened, thereby altering the rotational balance of the device. By eliminating the multiple-piece sleeve, the mounting devices described above reduce rotary imbalance during use. In this way, the devices can be circumferentially balanced during manufacture, and the devices will retain the balance during normal operation. 
         [0067]    It will be recognized by those skilled in the art that changes or modifications can be made to the above-described embodiments without departing from the broad inventive concept of the invention. It should therefore be understood that this invention is not limited to the particular embodiments described herein but is intended to include all changes and modifications that are within the scope and spirit of the invention as set forth in the following claims.