Abstract:
A torque fuse device having a bi-directional release mechanism that releases the torque carrying capability of the shafts upon torque overload is provided. The torque fuse device includes a sleeve, a hub positioned within the sleeve, and a hydraulic torque coupler. The sleeve and the hub are adapted to be coupled with two axially aligned shafts. The hub includes a feedback ring having at least one tooth formed therein. The hydraulic torque coupler includes a piston, a cylinder and a collet. The piston is positioned between the collet and the feedback ring and slides along an inclined surface of collet. One ore more fuse pins are selectively positioned between the tooth, the piston and the cylinder to frictionally engage the sleeve to the hub. Upon a torque overload condition, the pins release from the teeth thereby releasing the torque carrying capability of the shafts.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application No. 60/503,947, filed Sep. 17, 2003. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a torque fuse device for connecting two axially aligned shafts. More particularly, the torque fuse device includes a bi-directional torque release mechanism that releases the torque carrying capability of the shafts when a predetermined release torque is exceeded. 
   The use of torque release mechanisms to couple two axially aligned shafts is well known and used in a variety of different fields. For example, torque release mechanisms may be used in rolling steel mills and in watercraft drive applications. Specifically, torque overloads or spikes commonly occur when the steel mill rolls become jammed or when a propeller on a vessel strikes an object when traveling through a body of water. In either case, the torque release mechanism operates to release the connection between the two shafts when the aforementioned torque overload events occur to reduce or eliminate damage to the axially aligned shafts. 
   One type of torque release mechanism that may be used in either of these applications is referred to as a shear pin coupler. In this arrangement, a break pin is fastened between two flanges that extend from opposing axially aligned shafts. The break pin includes a weakened area that is positioned transverse to the longitudinal axis of the pin, which allows the pin to break at a predetermined loading point. Therefore, when a torque overload occurs, the pin breaks and the two shafts are permitted to move relative to each other. 
   Another known torque release mechanism utilizes friction to couple the shafts to one another. For example, U.S. Pat. No. 5,051,018 provides a coupling for coupling two mutually coaxial rotatable parts. The coupling includes a cylindrical bladder that is adapted to be filled with fluid so that it expands thereby frictionally engaging the two shafts. When the bladder to filled to a desirable level to achieve the necessary friction between the shafts, a plug is used top seal the fluid within the bladder. When a torque overload condition occurs, a blade cuts or otherwise removes the plug to release the hydraulic fluid from the bladder. The friction between the shafts is then reduced allowing the two shafts to move relative to one another. 
   While each of the torque release mechanisms described above operates to disengage the torque carrying capability between the external shafts, they each suffer from a number of drawbacks and deficiencies. For instance, the use of a break pin or temporary plug will force the user to replace the pin or plug each time the device is reset, which is time consuming and inefficient. In addition, the user must purchase and store replacement parts, which in turn increases the operational cost of the aforementioned devices. Further, the break pin may be subject to various vibratory loads within the connected machinery during operation. This repeated vibratory loading often times causes the break pins to fail prematurely, which results in an unintended shutdown of the equipment. 
   Some prior art devices will attempt to self-reset with each rotation after a torque overload has occurred. Specifically, the self-resetting devices reset by the rotation of a pair of fuse halves into a particular position where a tooth engages a hole or slot. However, the use of self-resetting devices may also be problematic. Each time the self-resetting device attempts to reset, a vibratory load is imposed on one or more of its components. Thus, if the machinery continues to rotate after a torque release has occurred, the self-resetting device may destroy itself due to is own vibratory loading. 
   Accordingly, there exists a need for a torque release mechanism that ameliorates the aforementioned drawbacks and deficiencies. The present invention fills these needs as well as other needs. 
   SUMMARY OF THE INVENTION 
   In order to overcome the above stated problems and limitations there is provided a torque fuse device that is adapted to couple two external shafts with each other, while providing a bi-directional release mechanism that releases the torque carrying capability of the shafts when a predetermined release torque is exceeded. 
   In general, the torque fuse device includes a sleeve, a hub positioned within the sleeve and a hydraulic torque coupler. In particular, the sleeve and the hub are adapted to be coupled with the two axially aligned shafts. The hub includes a feedback ring having at least one tooth formed therein. The hydraulic torque coupler includes a piston, a cylinder, a collet and one or more fuse pins. The collet is coupled with the sleeve and has at least one inclined surface. The piston is positioned between the collet and the feedback ring and is adapted to slide along the inclined surface of the collet. The fuse pins are adapted to be selectively positioned between the tooth, the piston and the cylinder to frictionally engage the sleeve with the hub. Each of the fuse pins include a tapered end and a leading edge that is slightly rounded. The piston and cylinder include a pair of opposing conical surfaces that are adapted to receive and come into contact with the tapered end of the pin. When a torque overload condition occurs, the pin releases from the tooth thereby releasing the torque carrying capability of the shafts. It will be understood that the pin is capable of releasing from either side of the tooth when a torque overload condition occurs. 
   The torque fuse device may also include a retainer ring having a series of apertures defined therein that correspond to the number of pins used in the torque fuse device. Each of the fuse pins are adapted to be positioned within the apertures formed in the retainer ring to maintain the spatial relationship between the pins around the circumference of the device. In addition, the torque fuse device may also include one or more adjustment screws that may be used to adjust how far each of the fuse pins are positioned within the piston and cylinder. Further, a lever arm may extend from each pin to allow a user to move the fuse pins to a set position. 
   Additional objects, advantages and novel features of the present invention will be set forth in part in the description which follows, and will in part become apparent to those in the practice of the invention, when considered with the attached figures. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The accompanying drawings form a part of the this specification and are to be read in conjunction therewith, wherein like reference numerals are employed to indicate like parts in the various views, and wherein: 
       FIG. 1  is a front perspective view of a torque fuse device according to the present invention; 
       FIG. 2  is an elevational view of a stub shaft or hub of the torque fuse device; 
       FIG. 3  is a perspective view of a cross-section taken along line  3 — 3  in  FIG. 2 ; 
       FIG. 4  is an enlarged elevational view of the cross-section shown in  FIG. 3 ; 
       FIG. 5  is an elevational view showing a plurality of fuse pins, a retainer ring, a feedback ring and a piston in accordance with the present invention; 
       FIG. 6  is a perspective view of the components illustrated in  FIG. 5  with portions broken away to show the fuse pins positioned between the piston and feedback ring; and 
       FIG. 7  is an enlarged view of the fuse pin positioned between the piston and cylinder as shown in  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings in detail, and initially to  FIGS. 1 and 3 , reference numeral  16  generally designates a torque fuse device constructed in accordance with a first embodiment of the present invention. In general, the torque fuse device  10  includes a sleeve  12  and a stub shaft or hub  14 . At least a portion of hub  14  is positioned within sleeve  12  and each are adapted to be coupled with a pair of axially aligned shafts (not shown). In accordance with the present invention, as best seen in  FIG. 4 , torque fuse device  10  also includes a hydraulic torque coupler  16  and one or more fuse pins  18  that operate to frictionally engage sleeve  12  with hub  14 . When a toque overload condition occurs, regardless of the direction that the shafts are rotating, torque fuse device  10  releases fuse pin  18 , which in turn disengages hub  14  from sleeve  12 . 
   As best seen in  FIGS. 3 and 4 , sleeve  12  is adapted to be fixedly coupled with a first external shaft (not shown). In particular, sleeve  12  includes an integrally formed circular end piece  20  having a plurality of apertures  22  defined therein to provide a location for the first external shaft to be coupled with sleeve  12  by one or more bolts or another suitable fastening device. In addition, sleeve  12  may be coupled to the first external shaft with a keyed fit joint or a press fit shaft joint. A center aperture  24  is defined in sleeve  12  to provide a location for rotatably coupling sleeve  12  and hub  14  with a shaft  34 . 
   As best seen in  FIGS. 2–4 , hub  14  is adapted to be fixedly coupled with a second external shaft (not shown) that may be axially aligned with the first external shaft described above. As with sleeve  12 , hub  14  includes an integrally formed circular end piece  26  having a plurality of apertures  28  defined therein to provide a location for the second external shaft to be coupled with hub  14  by one or more bolts or another suitable fastening device. In addition, hub  14  may be coupled with the second external shaft with a keyed fit joint or a press fit shaft joint. While the present embodiment describes hub  14  and sleeve  12  as having similar structural features for connecting to the first and second external shafts, it will be understood that the connection features for sleeve  12  and hub  14  may be different due to the type of shafts being connected to torque fuse device  10  or other structural considerations. Further, a center aperture  30  is defined in hub  14  and is adapted to be aligned with center aperture  24  formed in sleeve  12  when a trunk portion  32  of hub  14  is positioned within sleeve  12 . In addition, both center apertures  24 ,  30  are adapted to allow shaft  34  to be positioned therein to rotatably couple sleeve  12  with hub  14 . Shaft  34  extends through center apertures  24 ,  30  and is held into position by a pair of nuts  36  and lock washers  38  fastened to opposite ends of shaft  34 . A set of roller bearings  40  are positioned between shaft  34  and hub  14  to allow hub  14  to rotate freely about shaft  34 . 
   When hub  14  is positioned within sleeve  12 , it should be understood that there is a close fit between an outer diameter  42  of the hub  12  and an inner diameter  44  of sleeve  12 . The close fit allows the sleeve  12  to frictionally engage hub  14  with a relatively small amount of flexure of sleeve  12  toward hub  14 . Specifically, the distance between the outer diameter  42  and inner diameter may be between about 0.005 of an inch to about 0.025 of an inch, however, other distances are also contemplated and within the scope of the present invention. Given the close fit between sleeve  12  and hub  14 , a lubricant (not shown) may be positioned between the sleeve  12  and hub  14  and contained therein with a shaft seal ring  46 . 
   As best seen in  FIG. 4 , a radial ejector plate or feedback ring  48  is fixedly mounted to hub  14  and includes a side wall  50  and a top wall  52 . With additional reference to  FIG. 6 , top wall  52  has a set of teeth  54  that correspond to the number of fuse pins  18  used in the torque fuse device  10  and which are directed radially inward towards hub  14 . In addition, as best seen in  FIG. 7 , a threaded aperture  56  is formed in each tooth  54  to provide a location for a set of radial adjustment screws  58 . 
   As best seen in  FIG. 4 , hydraulic torque coupler  16  is positioned around an outer surface  60  of sleeve  12  and is used to apply the force necessary to frictionally engage sleeve  12  with hub  14 . In particular, hydraulic torque coupler  16  includes a cylinder  62 , a piston  64  and a collet  66 . Cylinder  62  is free to move along the taper in collet  66  until interference occurs between sleeve  12  and hub  14 . Collet  66  is fixedly mounted to sleeve  12 . Piston  64  is positioned between collet  66  and top wall  52  of feedback ring  48  and piston  64  is adapted to slide along the inclined surface of collet  66  to fictionally engage sleeve  12  and hub  14 . Cylinder  62  includes a hydraulic input  70  which permits fluid to be inserted into a hydraulic chamber  72  formed between cylinder  62  and piston  64 . It will be understood that hydraulic chamber  72  may be sealed with a seal ring  74  to ensure that the hydraulic fluid does not leak between piston  64  and cylinder  62 . 
   As best seen in  FIG. 7 , piston  64  and cylinder  62  include opposing conical surfaces  76 ,  77  that are adapted to receive one or more fuse pins  18 . Each fuse pin  18  includes a tapered end  78  so that fuse pin  18  may be received between and placed in contact with surfaces  76 ,  77 . Furthermore, a leading edge  80  of fuse pins  18  may be slightly rounded or curved to reduce the potential wear on fuse pins  18  when released from between cylinder  62  and piston  64 . Fuse pin  18  also includes an upper surface  82  that is adapted to contact an inner face  84  of tooth  54  and/or adjustment screw  58 . The longitudinal axis of each fuse pin  18  points radially and may be evenly spaced around the circumference of torque fuse device  10 . In order to allow a user to manipulate fuse pins  18  during a reset operation, a lever arm or handle  86  may be coupled with one or more of fuse pins  18 . While torque fuse device  10  utilizes twelve fuse pins in the present embodiment, it is within the scope of the present invention to use any number of fuse pins with torque fuse device  10 . Further, other types of fuse pins in addition to the one shown in the accompanying drawings are within the scope of the present invention so long as they are adapted to release from between the piston and cylinder upon a torque overload condition. 
   A pin retainer ring  88  is positioned around the outside of the cylinder  62  and piston  64  and fits within feedback ring  48 . Retainer ring  88  is not fixedly coupled with either cylinder  62 , piston  64  or feedback ring  48 , therefore it is free to rotate relative to each of these components. A series of holes  90  are defined in retainer ring  88  that correspond to the number of fuse pins present in device  10 . Each of the fuse pins  18  slide into their corresponding holes  90  so that the fuse pins do not fall out of the torque fuse device  10  once they have been released from between cylinder  62  and piston  64 . Retainer ring  88  also operates to maintain the circumferential position of fuse pins  18  relative to each other during the reset operation. As best seen in  FIGS. 5 and 7 , a snap ring  92  is positioned between feedback ring  48  and cylinder  62 . Snap ring  92  is radially thin and retainer ring  88  has a slot  94  formed therein to allow lever arm  86  to extend outwardly to a location where a user is able to manipulate fuse pins  18 . 
   In operation, torque fuse device  10  may be placed in a set position to couple the first and second shafts with each other. In particular, as best seen in  FIGS. 4 and 7 , the set position generally involves positioning each of fuse pins  18  between piston  64  and cylinder  62  to hold piston  64  and cylinder  62  apart and frictionally engage inner diameter  44  of sleeve  12  with outer diameter  42  of hub  14 . However, in order to position fuse pin  18  between piston  64  and cylinder  62 , a hydraulic fluid is pumped into chamber  72  through hydraulic input  70  to force piston  64  away from cylinder  62 . Using lever arm  86 , fuse pin  18  may then positioned so that its upper surface  82  rests on the inner face  84  of tooth  54 . Since piston  64  and cylinder  62  will have a tendency to push fuse pin  18  radially outward when pin  18  is placed between piston  64  and cylinder  62 , tooth  54  will prevent fuse pin  18  from being dislodged from torque fuse device  10 . Leading edge  80  of fuse pin  18  is then inserted between piston  64  and cylinder  62  so that conical surfaces  76 ,  77  are in contact with tapered end  78  of fuse pin  18 . While the size of tooth  54  generally determines the distance at which fuse pin  18  will rest within conical surfaces  76 ,  77 , adjustment screw  58  may be used to set fuse pin  18  deeper within piston  64  and cylinder  62  to push piston  64  and cylinder  62  even further apart. 
   As piston  64  and cylinder  62  are pushed apart by fuse pin  18 , piston  64  and cylinder  62  slide upwardly along the incline toward the edges of collet  66 . As piston  64  and cylinder  62  move up the collet  66  inclines, a stretching force in piston  64  and cylinder  62  creates radial pressure on collet  66 . In reaction to the radial pressure, sleeve  12  flexes toward and clamps onto trunk  32  of hub  14 . As sleeve  12  flexes toward hub  14 , inner diameter  44  of sleeve  12  will come into contact with outer diameter  42  of hub  14  so that sleeve  12  and hub  14  are frictionally engaged with one another. It will be understood and appreciated that the axial position of piston  64  and cylinder  62  on the incline of collet will determine the degree of frictional engagement between sleeve  12  and hub  14 . For instance, the friction created between inner diameter  44  of sleeve  12  and outer diameter  42  of hub  14  will increase as piston  64  and cylinder  62  are positioned further up the inclines of collet  66 . Once sleeve  12  and hub  14  are frictionally engaged with each other, torque may then be transferred between the first and second external shafts. 
   Upon the occurrence of a torque overload or torque spike, torque fuse device  10  operates to disengage the first and second shafts. Specifically, when a torque overload occurs, hub  14  and feedback ring  48  will rotate relative to sleeve  12 . The teeth  54  on feedback ring  48  will rotate relative to their corresponding fuse pins  18  so that fuse pins  18  slide out from under the teeth  54 . It will be understood that fuse pins  18  may slide out in either direction from their respective teeth  54 . As upper surface  82  of each fuse pin  18  is placed out of contact with inner face  84 , fuse pins  18  are thrust outwardly by piston  64  and cylinder  62  so that pins  18  are no longer positioned between piston  64  and cylinder  62 . This allows piston  64  and cylinder  62  to slide down the incline of collet  66 , which allows sleeve  12  to expand or flex outwardly away from outer diameter  42  of hub  14 . The frictional engagement is then released and sleeve  12  and hub  14  are free to rotate relative to one another. Thus, torque is no longer transmitted between the first and second external shafts until torque fuse device  10  is reset to the set position discussed above. 
   The present invention for a torque fuse device provides numerous advantages over the aforementioned prior art devices. For example, the torque fuse device allows for the fuse pins to release independent of the rotation of the external shafts. This is important for machinery used in steel rolling mills that periodically reverse operation and may jam in either direction. Another benefit of the torque fuse device is that it is not fatigued by vibratory loading imposed by the mated machinery. Unlike prior art devices that utilize break pins, plugs or other components to achieve a release condition, the fuse pins in the present invention are not damaged when released from between the piston and cylinder. Therefore, the torque fuse device does not require replacement of sacrificial pins, plugs or other parts that release by breaking. Moreover, the torque fuse device allows the sleeve and hub to rotate freely after the fuse pin is released. This allows for smooth operation of the machinery unlike self-resetting devices that produce a vibratory torque load every time they attempt to reset. 
   While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto, since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. Reasonable variation and modification are possible within the scope of the foregoing disclosure of the invention without departing from the spirit of the invention.