Abstract:
An isolator for a drill assembly that is mountable to a drill is presented. The isolator comprises an elongated outer member with an elongated inner member inserted within the outer member. An elastomer is interposed in the space between said inner member and said outer member. The isolator is connectable to a drill assembly at one end through the outer member and at the other end through the inner member. The isolator is capable of providing sound and vibration isolation when the drill assembly is mounted to a drill.

Description:
[0001]    This application takes priority from U.S. Provisional Patent Applications No. 61/582,689 filed on Jan. 3, 2012, Ser. No. 61/746,178 filed on Dec. 27, 2012, Ser. No. 61/746,186 filed on Dec. 27, 2012 each of which are incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    What is presented is a sound damping apparatus for drill assemblies. Drill assemblies can be, for example, a roof bolt drill assembly as used in underground mining operations. 
         [0003]    Drill assemblies are typically mounted to the chuck of a drill at one end. A drill bit is mounted on the opposing end of the drill assembly. The drill bit may be extended from a drilling machine, such as a roof bolting machine or the like, by interposing a drill rod or a series of drill rods which allows for drilling deeper holes into the target matter substrate—typically a wall or, in the case of mining operations, rock and/or minerals. 
         [0004]    One problem associated with the drilling operations is that a large amount of noise is generated. Studies have shown that, on average, drilling noise with roof bolting machines are the most significant contributor to a drilling machine operator&#39;s noise exposure. Thus, hearing loss remains one of the most common occupational illnesses for underground coal miners. 
         [0005]    Another problem associated with the drilling operation is mechanical failure of one or more of the various components of the drill assembly that typically results from one or more factors, such as, for example, the size limitations of the drill rod components, the mechanical forces encountered in the drilling operation and the rigid connections between the various components of the drill assembly. 
         [0006]    Thus, it would be desirable to have a drill assembly that overcomes the problems of known drill assemblies, particularly for drill assemblies used in roof bolt drilling operations. 
       SUMMARY 
       [0007]    An isolator for a drill assembly that is mountable to a drill is presented. The isolator comprises an elongated outer member that has an elongated inner member inserted within the outer member. An elastomer is interposed in the space between the inner member and the outer member. The isolator is connectable to the drill assembly at one end through the outer member and at the other end through the inner member. The isolator is capable of providing sound and vibration isolation when the drill assembly is mounted to the drill. 
         [0008]    In various embodiments, the elastomer is variously bonded to the inner member or bonded to both the inner member and the outer member. In some embodiments, the elastomer is bonded to the inner member and compression fit into the outer member. The elastomer can be made out of polyisoprene, a polyisoprene blend, butyl rubber, acryl rubber, polyurethane, flurorubber, polysulfide rubber, ethylene-propylene rubber (EPR and EPDM), Hypalon, chlorinated polyethylene, ethylene-vinyl acetate rubber, epichlorohydrin rubber, chloroprene rubber, silicone, or another heavily damped elastomer. 
         [0009]    Some embodiments of the isolator include features that act as displacement limiters to limit the relative axial or torsional movement between the inner member and the outer member of the isolator. This serves to limit the stress on the elastomer and the bonds between the elastomer and the inner member and the outer member. In some embodiments, the inner member comprises a shoulder that acts as an axial displacement limiter that limits the axial movement of the isolator. In other embodiments, the shoulder has a collar that acts as a torsional displacement limiter that limits the torsional movement of the isolator. In yet other embodiments the inner member has a shoulder and an outer facing annular bead, and the outer member has an inner facing annular bead located between the shoulder and the outer facing annular bead to limit the axial movement of the isolator between the shoulder and the outer facing annular bead. 
         [0010]    The shape of the components of the isolator can also be varied in different embodiments. In some embodiments, the inner member has an outer profile that is a hex shaped cross section perpendicular to the central axis of the isolator. In some embodiments that have this feature, the outer member has an inner profile that is a hex shaped cross section perpendicular to the central axis of the isolator. In other embodiments the inner member has an outer profile that is a square shaped cross section perpendicular to the central axis of the isolator. In yet other embodiments the inner member has an outer profile that is an elliptical shaped cross section perpendicular to the central axis of the isolator. Some benefits may also be seen in embodiments in which the inner member has an outer profile that is a tapered cross section in the central axis of the isolator. 
         [0011]    These and other aspects of the present invention will be more fully understood following a review of this specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    For a more complete understanding and appreciation of this invention, and its many advantages, reference will be made to the following detailed description taken in conjunction with the accompanying drawings. 
           [0013]      FIG. 1  shows a drill assembly with chuck and drill bit isolators installed on the chuck of a drilling machine; 
           [0014]      FIG. 2  is an exploded view of the isolator of  FIG. 1  focusing on the bit isolator showing the elements of the isolator that are coupled to the drill bit; 
           [0015]      FIG. 3A  is a view of the isolator of  FIG. 1 ; 
           [0016]      FIG. 3B  is a cross section of the isolator of  FIG. 3A ; 
           [0017]      FIG. 4  is a cross section of an isolator showing an embodiment that includes additional axial displacement limiter incorporated in the gap between the inner member and outer member of the isolator; 
           [0018]      FIG. 5A  is an embodiment of isolator that incorporates a collar on the shoulder of the inner member that acts as axial and torsional displacement limiters; 
           [0019]      FIG. 5B  is a close up of the isolator of  FIG. 5A  showing the isolator under maximum torsional load; 
           [0020]      FIG. 5C  is a close up of the isolator of  FIG. 5A  showing the isolator under maximum torsional and axial load; 
           [0021]      FIG. 6A  is another embodiment of isolator that incorporates a collar on the shoulder of the inner member that acts as axial and torsional displacement limiters; 
           [0022]      FIG. 6B  is a close up of the isolator of  FIG. 6A  showing the isolator under maximum torsional load; 
           [0023]      FIG. 6C  is a close up of the isolator of  FIG. 6A  showing the isolator under maximum torsional and axial load; 
           [0024]      FIG. 7A  is another embodiment of isolator that incorporates a collar on the shoulder of the inner member that acts as axial and torsional displacement limiters; 
           [0025]      FIG. 7B  is a close up of the isolator of  FIG. 7A  showing the isolator under maximum torsional load; 
           [0026]      FIG. 7C  is a close up of the isolator of  FIG. 7A  showing the isolator under maximum torsional and axial load; 
           [0027]      FIG. 8A  is an embodiment of isolator that incorporates a collar on the shoulder of the inner member that acts as axial displacement limiters; 
           [0028]      FIG. 8B  is a close up of the isolator of  FIG. 8A  showing the isolator under maximum axial load; 
           [0029]      FIG. 9A  shows an embodiment of inner member of an isolator in which the inner member has a hex shaped outer profile; 
           [0030]      FIG. 9B  shows a cross section of isolator having an inner member as shown in  FIG. 9A ; 
           [0031]      FIG. 10A  shows an embodiment of isolator in which both the inner member and outer member have a hex shaped outer profile and the inner member also has a tapered shape; 
           [0032]      FIG. 10B  is a cross section of the isolator of  FIG. 10A  showing the hex shaped outer profiles of the inner member and the outer member; 
           [0033]      FIG. 10C  is a cross section of the isolator of  FIG. 10A  showing the tapered shape of the inner member; 
           [0034]      FIG. 11A  is an embodiment of isolator in which both the outer profile of the inner member and the inner profile of the outer member are square shaped; 
           [0035]      FIG. 11B  is a cross section of the isolator of  FIG. 11A  showing the square shaped profiles of the inner member and the outer member; 
           [0036]      FIG. 11C  is a cross section of the isolator of  FIG. 11A ; 
           [0037]      FIG. 12A  is a cross-section of an embodiment of isolator in which the outer profile of the inner member is elliptical; 
           [0038]      FIG. 12B  is another cross section of the isolator of  FIG. 12A  showing the elliptical shaped outer profile of the inner member; 
           [0039]      FIG. 13A  shows a perspective view of the chuck of a drilling machine; and 
           [0040]      FIG. 13B  is a cross section of the chuck of  FIG. 13A  showing an isolator incorporated within the chuck. 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    Referring to the drawings, some of the reference numerals are used to designate the same or corresponding parts through several of the embodiments and figures shown and described. Corresponding parts are denoted in different embodiments with the addition of lowercase letters. Variations of corresponding parts in form or function that are depicted in the figures are described. It will be understood that variations in the embodiments can generally be interchanged without deviating from the invention. 
         [0042]    In rock drilling operations, one notable source of noise generation is vibration of the drill rods. There are three fundamental ways to reduce these vibrations, and the resulting noise: reduce the source of the vibration, attenuate the structural vibration using isolation or damping treatments, or attenuate the airborne noise by using barriers or absorbers. The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) has conducted various studies to quantify the vibration levels of the components associated with drilling roof bolt bore holes. The results show a major source of noise is located just above the chuck and a second major source of noise centered on the drill rod, below the interface of the drill rod and the media which the drill is cutting into. These two areas were also shown to have high vibration levels. Therefore vibration isolation and damping are considered to be appropriate noise control methods. 
         [0043]    Most of the noise emitted during drilling of rock media is due to noise radiated by the drill rods and chuck in response to forces at the drill bit-media interface. During drilling, the vibratory forces, generated at the drill bit-media interface, are transmitted to the drill rods and the chuck causing them to vibrate. Assuming linear viscous damping, the response of the structure is governed by: 
         [0000]      [ M]X″+[C]X′+[K]X=[F]   (1)
 
         [0000]    where [M], [C], and [K] are the mass matrix, damping matrix, and stiffness of the structure; [F] is the vector of applied forces; and X″, X′, and X are the acceleration, velocity, and displacement response of the structure. Using the Laplace transform, substituting s=jω, and rearranging Equation (1) to solve for X yields: 
         [0000]      [ X]=[K+jωC−ω   2   M]   −1   [F]   (2)
 
         [0000]    where ω is the forcing frequency in units of rad/s and j denotes the √−1. 
         [0044]    Assuming the damping is small enough to be ignored compared to the stiffness and the mass times the frequency squared, Equation (2) is reduced to: 
         [0000]      [ X]=[K−ω   2   M]   −1   [F]   (3)
 
         [0045]    For a fixed stiffness, Equation (3) shows that the response decreases with frequency squared once the frequency is well beyond the value where the ω 2 M term exceeds the stiffness, K. Furthermore, if the stiffness of the system is reduced, the frequency at which the ω 2 M term exceeds the stiffness will decrease. Thus, isolation is achieved by decreasing the stiffness of the system. The stiffness of the system can be decreased by adding compliance via an isolation device. This would decrease the response of the system to high frequency input forces. 
         [0046]    For a vibrating object, the sound power radiated is given by the following: 
         [0000]        W=ρcS             v   2           σ rad   (4)
 
         [0000]    where W is the sound power radiated, &lt;v 2 &gt; is the mean-squared vibration velocity, S is the vibrating area, ρ is the air density (km/m 3 ), c is the speed of sound (m/s), and σ rad  is the radiation efficiency. Equation (4) shows that the sound power radiated by a vibrating structure will be reduced if the surface-averaged mean-squared vibration velocity is reduced. Because the vibration velocity is directly related to the displacement response of the system, reducing the displacement response of the system will reduce the radiated noise. This can be accomplished with a properly designed vibration isolator. 
         [0047]    As will be appreciated from the description and drawings set forth herein, such a vibration isolator provides for reduced noise during a drilling operation, as well as improved mechanical durability and flexibility of the drill assembly during the drilling operation. 
         [0048]      FIG. 1  illustrates a drill assembly  10  (e.g. a roof drill bit assembly) that incorporates embodiments of an isolator  12  that incorporates some of the vibration and sound isolation principles outlined above and that operates as both a chuck isolator and a bit isolator. It will be appreciated that the invention is not limited to a roof bolt drill assembly and that drill assemblies for other applications would equally benefit, but such an assembly is provided for purposes of illustration. In the embodiment shown in  FIG. 1 , the chuck isolator and the bit isolator are identical, eliminating the need to have two complex metal components. Because a single design can be used, the production volume is expected to increase, which would reduce the cost of the isolators. It will be appreciated that any of the variations of isolators shown herein, and their equivalents, could be used interchangeably as bit isolators or chuck isolators as appropriate. 
         [0049]    The drill assembly  10  includes one or more drill rods  14  that are removably connected between the isolators  12 . The isolator  12  that is functioning as a bit isolator is removably connected a drill bit  16  that is removably connected to the other end of the bit isolator. The drill assembly  10  also includes a means for driving the drill assembly  10  which may be, for example, a drill or drilling machine  18 . The entire drill assembly  10  is mounted to a chuck  20  on the drilling machine  18  by removably attaching the isolator  12  that is serving as a chuck isolator to the chuck  20 . While the drill assembly  10  will see the most improved reduction in vibration and noise with the inclusion of two isolators  12 —the chuck isolator and bit isolator, it will be understood that significant improvement to vibration and noise reduction can be achieved with the inclusion of only one chuck isolator or bit isolator. 
         [0050]    As best shown by comparing  FIGS. 1 and 2 , a bit coupler  24  is used to connect the drill bit  16  to the isolator  12 , making it a bit isolator. If needed, a drill rod spacer  22  is interposed between the bit coupler  24  and the isolator  12 . Because the bit coupler  24  is not integral to the isolator  12 , if the bit coupler  24  wears, only the bit coupler  24  needs to be replaced, not the entire isolator  12 . These elements are not necessary in every embodiment, and it will be understood that the drill bit  16  could be mounted directly to the isolator  12  in some embodiments. In fact, embodiments could be manufactured in which the isolator  12  serves specifically as a bit isolator or specifically as a chuck isolator, but it is understood that such embodiments limit the manufacturing economies of scale. One of the limitations of designing these isolators  12  is that the isolator  12  cannot be wider than the drill bit  16 , because an isolator  12  located directly behind the drill bit  16  should not impede the progress of the drill bit  16  through the drilled medium, otherwise the isolator  12  will limit the depth to which the drill can operate. 
         [0051]    In some applications, the drill rods  14  may be eliminated if no extension of the drill bit  16  is required. In fact, in some applications, a single isolator  12 , whether a chuck isolator or bit isolator, by itself may provide sufficient extension of the drill bit  16  such that the drill assembly  10  would then comprise the drill bit  16  mounted to the isolator  12  which is mounted to the chuck  20  of the assembly of the drilling machine  18 . In these instances, the chosen isolator  12  will act as both a chuck isolator and a bit isolator as defined herein. A consideration of the bit isolator is that this isolator should not be wider than the drill bit  16 , so as not to interfere with drilling operations. 
         [0052]    As shown in  FIGS. 3A and 3B , the isolator  12  comprises: an inner member  26 , an outer member  28 , and an elastomer  30 . The elastomer  30  provides compliance in multiple directions and provides sound and vibration isolation. The outer member  28  and the inner member  26  are typically machined out of 4130/4140 steel and heat treated to 35 HRC. However, it will be understood that other materials may be utilized if the particular applications requires it. The elastomer  30  can be any appropriate material including polyisoprene, a polyisoprene blend, butyl rubber, acryl rubber, polyurethane, flurorubber, polysulfide rubber, ethylene-propylene rubber (EPR and EPDM), Hypalon, chlorinated polyethylene, ethylene-vinyl acetate rubber, epichlorohydrin rubber, chloroprene rubber, silicone, or other heavily damped elastomer such as those that may be manufactured by Corry Rubber Corporation of Corry, Pa. The dynamic modulus and loss factor (damping) of the elastomer are determined for optimal noise and vibration isolation. 
         [0053]    In the embodiment shown in  FIGS. 1 through 3B , the elastomer  30  is chemically bonded between the inner member  26  and the outer member  28  in a mold machine. As best shown by comparing  FIGS. 3A and 3B , in this embodiment, the isolator is manufactured by arranging the inner member  26  and outer member  28  into a mold in their desired final locations. The mold accommodates a device to ensure the inner member  26  maintains a hollow channel. Liquid elastomer  30  is injected into the machine to fill the spaces between the inner member  26  and the outer member  28 . In the embodiment shown in  FIGS. 1  though  3 B, the outer member  28  incorporates a series of holes  32  through which elastomer  30  can flow, providing additional surface area on the outer member  28  to which the elastomer  30  can bond, thereby increasing the strength of the bond and making the outer member  28  more secure within the isolator. The holes  32  are not required and embodiments without such holes  32  would still fulfill the requirements of the isolators described herein. 
         [0054]    It is also possible to chemically bond the elastomer  30  to just the inner member  26  and then compress the elastomer  30  into the outer member  28 . The embodiments in which the elastomer  30  is bonded to both the inner member  26  and the outer member  28  are preferred in applications that require their superior bond strength and load carrying capacity, over embodiments in which the elastomer  30  is just bonded to the inner member  26 . However, elastomer bonded to an inner member  26  and subsequently pressed into an outer member  28  places the elastomer in pre-compression. Elastomer in pre-compression can have a significant improvement in fatigue life (the result of a net compression strain that must be overcome before the elastomer can be in a state of tension or shear). 
         [0055]    An end cap  34  is joined to the outer member  28  after the elastomer  30  is bonded to the outer member  28  and the isolator  12  is ejected from the mold. The end cap is typically welded to the outer member, but it should be understood that any permanent joining means could be used. In the embodiment shown in  FIG. 2 , both ends of the isolator  12  have male ends, allowing the isolator  12  to be positioned along any point of the drill rods  14 , or act as a replacement to a drill rod  14  if needed. Having both ends being male also allows the isolator  12  to be oriented in either direction without adversely affecting performance. It will be understood, that the type of end connector can be something besides male ends, such as female ends, male or female screw threads, or any other type of connector. In addition, each end could have a different type of connector, however doing so could limit the orientation of the isolator  12  within the drill assembly  10 . 
         [0056]    The small gap  36 , best seen in  FIGS. 3A and 3B , between the outer member  28  and the shoulder  38  formed on the inner member  26  acts as an axial displacement limiter protecting the elastomer  30  from overload. This serves to limit the stress on the elastomer  30  and the bonds between the elastomer  30  and the inner member  26  and the outer member  28 . When the drilling machine  18  is in operation, and the drill bit  16  is pressed against the matter to be drilled, axial thrust force is applied to the drill bit  16  and transmitted through the isolator  12 . In some degree the axial thrust force is resisted by the characteristics of the elastomer  30  itself, but some axial thrust compliance will be experienced which will shorten the gap  36 . However, if the force is large enough, the extent of this compliance will be limited by the gap  36  because the outer member  28  will bottom out against the shoulder  38  on the inner member  26  and actively eliminate the gap  36 . When the gap  36  is eliminated, metal-on-metal contact between the inner member  26  and the outer member  28  will support the elastomer  30  and the elastomer  30  will experience no further axial thrust compliance. When the axial thrust force is relieved, the elastomer  30  will return the inner member  26  and the outer member  28  to their previous positions, restoring the gap  36 . 
         [0057]    The isolator  12  reduces the amount of vibration and noise generated during drilling operations. The isolator  12  also reduces the potential for mechanical failure of the drill assembly  10  during operation. Specifically, the elastomer  30  in the isolator  12  increases the flexibility of the drill assembly  10 . For example, drill assemblies  10  without such isolators  12  have a stiff or rigid mechanical connection between the chuck  20  of the drill machine  18  and the drill rods  16 . During operation, these components experience large mechanical stresses and/or forces due to the nature of the drilling process. Thus, it will be appreciated that the isolator  12  advantageously reduces the mechanical stresses and/or forces that the drill assembly  10  components are subjected to as a result of the elastomer  30 , providing for improved overall flexibility between the various components of the drill assembly  10 . 
         [0058]    The elastomer  30  also provides torsional compliance in the direction of rotation of the drill assembly  10 . In addition, the nature of the elastomer  30  provides radial and cocking compliance to reduce the overall stiffness of the drill assembly  10  to better react to bending loads imposed during operation. The stiffness is inherent in the elastomer  30 , meaning that it would take a large amount of force for the elastomer  30  to be displaced, if at all. Therefore, it would take extreme circumstances to actually cause substantial movement, increasing the overall life of the drill assembly  10 . 
         [0059]    If additional axial stiffness is required by a particular application,  FIG. 4  shows an embodiment of isolator  12   a  in which the elastomer  30   a  is extended to fill the gap  36   a  between the inner member  26   a  and the outer member  28   a . In this case, a small contour is shaped into the elastomer  30   a  within the gap  36   a  to provide elastomer to elastomer snubbing upon axial overload. 
         [0060]    Variations of isolators providing torsional displacement limiter are also possible. For example, in the embodiment of isolator  12   b  shown in  FIG. 5A , a collar  40   b  is joined onto the shoulder  38   b  on the inner member  26   b . Typically the collar  40   b  is welded or formed onto the shoulder, but it will be understood that other permanent joining methodologies may work. The outer member  28   b  is cut to match the profile of the collar  40   b . As shown in  FIG. 5B , when the drill is in operation, the isolator  12   b  will experience twisting torsional force. The compliance inherent in the elastomer  30   b  will allow the inner member  26   b  and the outer member  28   b  to rotate relative to each other. However, some stiffness is inherent in the elastomer  30   b , such that it would take some amount of force for the elastomer  30   b  to be displaced, if at all. Therefore, substantial relative movement of the inner member  26   b  to the outer member  28   b  would occur only in extreme circumstances. Nevertheless, rotation will be limited by the distance between the collar  40   b  and the side wall of the outer member  28   b . This helps ensure that the elastomer  30   b  is not under enough strain to actually damage the isolator  12   b . Similarly, as shown in  FIG. 5C , the shoulder  38   b , still acts as a displacement limiter in the axial direction as with the embodiments described above to limit the stress on the elastomer  30   b  and the bonds between the elastomer  30   b  and the inner member  26   b  and the outer member  28   b.    
         [0061]    Another variation of isolator  12   c  incorporating torsional and axial displacement limiters is shown in  FIGS. 6A-6C . In this embodiment of isolator  12   c , the collar  40   c  is joined onto the shoulder  38   c  on the inner member  26   c  at a straight 45-degree angle, relative to the central axis of the isolator  12   c . Typically the collar  40   c  is welded or formed onto the shoulder, but it will be understood that other permanent joining means are acceptable. The outer member  28   c  is cut to match the profile of the collar  40   c . As shown in  FIG. 6B , when the drill is in operation, the isolator  12   c  will experience twisting torsional force. The compliance inherent in the elastomer  30   c  will allow the inner member  26   c  and the outer member  28   c  to rotate relative to each other. However, stiffness is inherent in the elastomer  30   c , meaning that it would take a large amount of force for the elastomer  30   c  to be displaced, if at all. Therefore substantial relative movement of the inner member  26   c  to the outer member  28   c  would occur only in extreme circumstances. Nevertheless, this rotation will be limited by the distance between the collar  40   c  and the side wall of the outer member  28   c . This helps ensure that the elastomer  30   c  is not under so much strain as to damage the isolator  12   c . Similarly, as shown in  FIG. 6C , the shoulder  38   c , still acts as a displacement limiter in the axial direction as with the embodiments described earlier. It will be understood that the collar  40   c  is not limited to the 45-degree angle shown and that other angles would serve the same purpose shown. 
         [0062]      FIGS. 7A-7C  show yet another variation of isolator  12   d  that incorporates torsional and axial displacement limiters. In this embodiment of isolator  12   d , the collar  40   d  is joined to the shoulder  38   d  on the inner member  26   c  as an axial extension that protrudes into the area of the outer member  28   d  much more than other embodiments. Typically the collar  40   d  is welded or formed onto the shoulder, but it will be understood that other permanent joining means are acceptable. The outer member  28   d  is cut to match the profile of the collar  40   d . As shown in  FIG. 7B , when the drill is in operation, the isolator  12   d  will experience twisting torsional force. The compliance inherent in the elastomer  30   d  will allow the inner member  26   d  and the outer member  28   d  to rotate relative to each other. However, stiffness is inherent in the elastomer  30   d , meaning that it would take a large amount of force for the elastomer  30   d  to be displaced, if at all. Therefore, substantial relative movement of the inner member  26   d  to the outer member  28   d  would occur only in extreme circumstances. Nevertheless, the rotation will be limited by the distance between the collar  40   d  and the side wall of the outer member  28   d , helping to ensure that the elastomer  30   d  is not under so much strain as to damage the isolator  12   d . Similarly, as shown in  FIG. 7C , the shoulder  38   d , still acts as a displacement limiter in the axial direction as with the embodiments described earlier. 
         [0063]    As shown in  FIGS. 8A and 8B , it is also possible to provide axial displacement limits in isolators  12   e  in both directions. In this embodiment of isolator  12   e , the inner member  26   e  has an outer-facing annular bead  42   e  is joined on its exterior, while the outer member  28   e  has an opposing inner-facing annular bead  44   e  located between the shoulder  38   e  and the outer-facing annular bead  42   e  in the assembled isolator  12   e . Typically the outer-facing annular bead  44   e  is welded or formed on the exterior, but it will be understood that other permanent joining means are acceptable. When the isolator  12   e  experiences axial deflection, the displacement between the inner member  26   b  and the outer member  28   e  is limited by the displacement of the inner-facing annular bead  44   e  between the clearance between the shoulder  38   e  and the outer-facing annular bead  42   e.    
         [0064]    Other embodiments of isolators comprise variations of other elements to provide variations in torsional and axial load capacity. For example, the embodiment depicted in  FIGS. 9A and 9B  shows the inner member  26   f  having an outer profile that is hex-shaped. In this instance if the elastomer  30   f  is bonded only to the inner member  26   f  and the outer member  28   f  is compression fit into the inner member  26   f  (as discussed earlier), the elastomer  30   f  experiences both compression stress as well as shear stress during operation. Upon axial loading, the elastomer is placed in a combined state of compression and shear, which improves fatigue life and increases stiffness and load capacity.  FIG. 9B  shows an example of an isolator  12   f  with a inner member  26   f  having this feature. 
         [0065]    Another variation of isolator  12   g  is depicted in  FIGS. 10A-10C . In this embodiment, the inner member  26   g  has an outer profile, having a hex shaped cross-section, that is perpendicular to the central axis and the outer member  28   g  has a matching cross-section. Moreover, the inner member  26   g  is tapered along the central axis as shown in  FIG. 10C . This embodiment has increased load capacity in both torsion and axial directions, since the elastomer is placed in a combined state of compression and shear. The inner member  26   g  can be made smaller and still carry the required loads of larger embodiments that lack these features. 
         [0066]      FIGS. 11A-11C  depict another embodiment of isolator  12   h  in which the inner member  26   h  has an outer profile, having a square shaped cross-section, that is perpendicular to the central axis. Moreover, the outer member  28   h  has a matching inner profile with a circular outer profile. This embodiment of isolator  12   h  has increased torsional stiffness and therefore is suited for applications that require higher torque capacity. 
         [0067]    In the embodiment of isolator  12   i  depicted in  FIGS. 12A and 12B , the inner member  261  has an inner profile, having a circular cross-section, that is perpendicular to the central axis, but an outer profile having an elliptical cross-section. The outer member  281  has both an inner and outer profile having a circular cross-section. In this embodiment, when the isolator  12   i  is in operation, the torque experienced by the isolator  121  places the elastomer  301  in compression which increases the overall torque capacity of the isolator  121 . 
         [0068]    While all of the isolator embodiments discussed so far have been described as chuck isolators that are additions mounting onto the chuck of a drilling machine, it will be appreciated that any of the chuck isolator embodiments described above can be incorporated directly into the chuck of the drilling machine.  FIGS. 13A and 13B  show one embodiment of drilling machine  18   j  that incorporates a variation of the isolator  12   j , shown in  FIG. 3A , directly into the chuck  20   j  of a drilling machine  18   j . Any of the other embodiments of chuck isolator shown and described herein, and their variations, can be similarly incorporated into drilling machines. 
         [0069]    This invention has been described with reference to several preferred embodiments. Many modifications and alterations will occur to others upon reading and understanding the preceding specification. It is intended that the invention be construed as including all such alterations and modifications in so far as they come within the scope of the appended claims or the equivalents of these claims.