Abstract:
The head nut assembly for gyratory crusher which includes a shaft having a lower portion, a tapered middle portion and a threaded upper portion. The threaded upper portion extends above the tapered portion. A mantle encompasses the middle tapered portion and has a correspondingly tapered internal side. The internal side is in generally continuous supportive engagement with the shaft middle portion. The mantle additionally has an upper side. A head nut is threadably secured to the upper portion of the shaft. The head nut has a lower face, where at least one bore extends upwardly into the lower face. An annular ring is disposed around the shaft between the mantle and the head nut. The ring has a lower surface coupled with the upper side of the mantle so as to prevent relative rotational movement between the mantle and the ring. An upper surface on the ring is contiguous with the lower face of the head nut. At least one key is disposed between the head nut and the annular ring. The key is completely captured inside the head nut bore and acts to couple the ring to the head nut and prevent relative rotational movement between the ring and the head nut.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a divisional of U.S. patent application Ser. No. 09/451,531 filed on Dec. 1, 1999 now U.S. Pat. No. 6,299,083 and claims priority from U.S. Provisional Application Serial No. 60/136,899 filed on Jun. 1, 1999 both of which are incorporated by reference in their entirety herein. 
    
    
     BACKGROUND OF THE INVENTION 
     Gyratory type crushers are used in the mining industry for reducing ore to a predetermined size for further processing. These style of crushers have taken over most large hard-ore and mineral-crushing applications which has made them an integral part of the mining industry. Typically, a gyratory crusher comprises a stationary conical bowl (or mortar) which opens upwardly and has an annular opening in its top to receive feed material. A conical pestle, opening downwardly, is disposed within the center of the bowl. The pestle is eccentrically oscillated for gyratory crushing movement with respect to the bowl. The conical angles of the pestle and bowl are such that the width of the passage decreases towards the bottom of the working faces and may be adjusted to define the smallest diameter of product ore. The oscillatory motion causes impact with the pestle and bowl, as a piece of ore is caught between the working faces of the bowl and pestle. Furthermore, each bowl and pestle includes a liner assembly replaceably mounted on the working faces, these liners define the actual crushing surface. 
     The pestle is formed by the liner, called a mantle fitted around the outside of a main shaft. The mantle provides a replaceable wearing surface. A threaded section on the shaft (or a threaded sleeve fit over the shaft) above the tapered portion of the shaft is provided for receiving a head nut. The head nut forces the mantle downward onto the tapered portion of the shaft, and is forceably tightened against the top of the mantle. Tightening prevents relative rotational movement between the head nut and the mantle. When the crusher is put into operation, the large forces involved in crushing stone cause a differential rotational movement between the shaft and the mantle. The head nut on the threaded section of the shaft is also caused to rotate relative to the shaft, in a direction which acts to further tighten the head nut onto the mantle. Thus, the rotational movement of the head nut relative to the shaft causes a large force to be transmitted in a downward direction from the head nut so as to forceably wedge the mantle onto the tapered portion of the shaft, securing the mantle to the shaft. The force also causes the bottom surface of the head nut to be pressed tightly against the top surface of the mantle such that the frictional force between the head nut and the mantle is quite large. 
     The frictional force between the head nut and the mantle makes it difficult to loosen the head nut by turning. Additionally, during operation of the crusher the crushing surface of the mantle is subjected to a hammering action by repeated impact of the rock or other material being crushed. This hammering action causes the working surface of the mantle to expand by cold working. The expansion of the mantle works to increase the fictional force between the head nut and the mantle. The cumulative effect of the tremendous frictional force between the head nut and the mantle is that it becomes impossible to loosen the head nut by turning it. 
     It is, however, necessary to remove the head nut when the mantles become worn and need replacing. Since it is not practical to loosen the head nut by turning, it must be cut from the threaded section of the shaft (as with a cutting torch). Removing the head nut in this manner damages the head nut beyond repair so that it cannot be used again. The threaded section of the shaft (or sleeve) is also easily damaged when removing the head nut in this fashion, such that the threaded shaft must be repaired, or possibly replaced. Thus, the cost associated with removing the head nut to replace worn mantles becomes excessive. 
     A solution to this problem proposed in prior art is to provide a burning ring between the mantle and the head nut. The burning ring is adapted so as to engage to the upper surface of the mantle and the lower surface of the head nut. When the mantle is being replaced, the burning ring is cut with a cutting torch, relieving the frictional forces bearing on the head nut. The threaded portion of the head nut may then easily be unscrewed from the shaft and the mantle can be removed. 
     The main method taught in prior art of affixing the burning ring to the head nut as well as the burning ring to the mantle is using keying systems. Keys are placed between the surfaces of the head nut and burning ring and between the head nut and the mantle. Typically, the keys are inserted between the components of the head nut assembly (head nut, burning ring, top of mantle) after the components are mounted on the main shaft. A common method is to form a semicircular slot running radially on each of the interfacing component surfaces, align the slots, and then place a circular pin into the slots so as to couple the surfaces together. Other shapes of slots or grooves are also used in conjunction with a key or bolt inserted after the slotted surfaces are aligned. With this arrangement, the key must be welded to the interfacing components in order for the key to be held in place. Only small welds are possible, since large welds would be on or near the exposed crushing surfaces. If the welds are on the crushing surface they are subject to breaking, allowing the key to come loose. 
     Other methods of attachments utilize the key as the “cutting piece.” The “cutting piece” is cut by the operator to separate the components. All of these methods require that the key be exposed to the interior of the crusher. Using exposed keys to connect the head nut, burning ring and mantle is problematic, since the interior of the crusher is a harsh environment which very often results in the keys being knocked out from between the components, uncoupling the components. 
     If the interface between the head nut and the burning ring or the interface between the burning ring and the mantle become uncoupled, the self-tightening feature of the head nut is lost, since the mantle no longer transfers the twisting force (which occurs when being impacted by rock) to the head nut. The mantle can loosen from the main shaft. If the gyratory crusher is not shut off, the free spinning mantle can cause extensive damage to the crusher. The mantle may crack or break, requiring replacement, or the mantle may twist with respect to the shaft, and gouge the shaft. Alternatively, the mantle may move vertically along the shaft, causing damage to the head nut or the threads of the head nut. All of these can result in extensive repairs at a great cost and with long machine downtime. At the very least, the separation of the assembly components make it necessary to turn off the machine, remove the crushing material and replace the connection, which requires a good deal of labor and lost time. 
     Additionally, installation problems arise when the components must be aligned after they are mounted to the shaft of the crusher to accommodate a key. The problems occur because the head nut assembly must be tightened to prevent excess “play” between the components. The key cannot be placed between the faces of the components when too much space exists between the components. When the head nut is torqued to the proper level, the slots in the component faces may not line up to accommodate the key. The operator must then untorque the head nut, realign the components, and re-torque the head nut until the correct alignment is attained. 
     An alternative connecting method depicted in prior art shows the coupling of the head nut to the burning ring by welding. Although welding forms a tight bond between the components and eliminates alignment problems, distortion of the head nut can result. Distortion is caused by the heat required to weld the head nut to secure the head nut to the burning ring and also to plasma torch cut the welds to free the head nut from the burning ring. Distortion of the head nut prevents the head nut from easily being removed from the shaft, and reused. Instead, the head nut must be cut off and replaced, eliminating any advantage gained by using the burning ring in conjunction with the head nut. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention is a method for securing a mantle to a shaft. The mantle has a tapered internal side and an upper side and the shaft has a lower portion and a middle portion correspondingly tapered to be in general contiguous supportive engagement with the mantle internal side and additionally has a threaded upper portion extending above the mantle. An annular ring is disposed around the shaft above the mantle. A head nut is threaded to the upper portion of the shaft above the annular ring. The head nut is secured to the ring using a key totally captured inside the head nut in the annular ring. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a vertical cross-sectional view of the preferred embodiment of a gyratory crusher equipped with the crusher shaft and inventive head nut assembly. 
     FIG. 2 shows a vertical cross-sectional view of the crusher shaft of the gyratory crusher shown in FIG. 1 utilizing the inventive head nut assembly. 
     FIG. 3 shows a partial cross-sectional view of the crusher shaft and inventive head nut assembly shown in FIG.  2 . 
     FIG. 4 shows an exploded partial view of the preferred embodiment of a gyratory crusher with the inventive head nut assembly. 
     FIG. 5 shows an exploded side view of an alternate embodiment of the inventive head nut assembly. 
     FIG. 5A shows an exploded side view of an alternate embodiment of the inventive head nut assembly. 
     FIG. 5B shows an exploded side view of an alternate embodiment of the inventive head nut assembly. 
     FIG. 6 shows an exploded perspective view of an alternate embodiment of the inventive head nut assembly. 
     FIG. 7 is a cross sectional view of the head nut assembly shown after wearing due to the crushing process. 
    
    
     DETAILED DESCRIPTION 
     A gyratory crusher embodying the invention is shown generally at  10  in FIG.  1 . The gyratory crusher includes a lower frame  12 , an upper frame  14 , a top frame  16 , and a main shaft  18 . The lower frame  12  is provided with a bottom hub  20  opening upwards, and the upper frame  14  is provided with a top hub  22  opening downwards. 
     The shaft  18  includes a lower journal portion  24 , a middle tapered portion  26  extending from the lower journal portion  24  and an upper journal portion  28  converging from the middle tapered portion  26 . An eccentric sleeve bearing  30  is fitted about the lower journal portion  24 . The lower journal portion  24  and the eccentric sleeve bearing  30  are disposed within the bottom hub  20  so as to be rotatable within the bottom hub  20 . A bearing sleeve  32  is fitted about the upper journal portion  28 . The bearing sleeve  32  and the upper journal portion  28  are disposed in the top hub  22  so as to be rotatable within the top hub  22 . When the eccentric  30  is rotated the shaft  18  is moved transversely with respect to its axis. Thus, the eccentric sleeve bearing  30  causes the shaft to “gyrate” or move eccentrically. Since the eccentric  30  is located in the bottom hub  20 , and the shaft  18  is locked in the top hub  22 , the travel distance of the shaft  18  decreases from the end of the shaft  18  in the bottom hub  20  to the end of the shaft  18  disposed in the top hub  22 . Additionally, the oscillating motion of the shaft  18  within the gyratory crusher causes the shaft  18  to slowly rotate. 
     A mantle  34  is disposed around the outside of the tapered portion  26  of the shaft  18 . The mantle  34  substantially conforms to the shape of the taper and is typically manufactured of manganese steel, although a person skilled in the art would realize that other metals may be used, including other alloy steels. The upper frame  14  surrounds the shaft  18  and mantle  34 , forming a crushing chamber  36  disposed substantially between the upper frame  14  and the mantle  34 . To operate the crusher, the crushing chamber  36  is filled with rock (or other material) through the top frame  16 . The shaft  18  is oscillated eccentrically. The eccentric motion of the shaft  18  causes the rock to be compressed between the walls of the crushing chamber (including the mantle  34  and the upper frame  14 ), as well as against other rock in the crushing chamber  36 . The tapered shape of the mantle  34 , the inward sloping walls of the upper frame  14  as well as the increasing transverse movement of the shaft  18  towards the lower end of the shaft causes the area of the crushing chamber  36  to decrease as the rock falls towards the bottom of the chamber  36 . Thus, the rock is broken into smaller and smaller pieces until it is removed from the bottom of the crusher. The mantle  34  is cold worked by the impinging rock in the crushing chamber  36 , causing the mantle  34  to expand. The mantle  34  also experiences rotational forces (caused by the crushing material as it is compressed against the mantle  34  during the crushing process) counter to the rotational direction of the shaft  18 . 
     To support the mantle  34  on the main shaft  18 , a filler or backing material  38  (known to those skilled in the art, such as using a zincing process) is poured between the shaft  18  and the mantle  34  as shown in FIG.  2 . The filler material  38  is allowed to cool and solidify and thereby maintains a contiguous connection between the shaft  18  and the mantle  34 . The material  38  adheres to the inside of the mantle  34 , however, it does not adhere to the main shaft  18 . The filler  38  is used to provide a tight clearance between the mantle  34  and the shaft  18 , helping to secure the two pieces together. The main securing mechanism, however, is provided by connecting the upper journal portion  28  of the shaft  18  to the mantle  34 . 
     Bearing sleeve  32  extends coextensively with the upper journal portion  28  of the shaft  18 , with its lower end  40  disposed proximate to the top end  42  of the tapered portion  26  of the shaft  18 . As shown in FIG. 3, the lower end  40  of the bearing sleeve  32  includes an externally threaded annular shoulder  44 . The threaded shoulder  44  is secured to the top end  42  of the mantle  34  through a head nut assembly  50 . The head nut assembly  50  includes an annular head nut  52 , an annular burning ring  54  and keys  56 A and  56 B. The head nut  52  is internally threaded so as to be received by the threaded shoulder  44  of the bearing sleeve  32 . Although the preferred embodiment of the invention threads the head nut  52  to the bearing sleeve  32 , a person skilled in the art would realize that other embodiments conform to the spirit of the invention, including threading the head nut  52  directly to the upper journal portion  28  of the shaft  18 . It is important to counter the rotational forces caused by the crushing action and maintain the mantle  34  in the same relative rotational position with the shaft  18 . If this is not done, the mantle  34  can gouge the shaft  18 , or break off the shaft  18  completely. The head nut  52  provides a downward force on the mantle  34  which forces the mantle  34  and filler  38  against the shaft  18 , preventing the mantle  34  from rotating with respect to the shaft  18 . Any rotational motion between the shaft  18  and the mantle  34  causes the nut  52  to tighten, adding additional downward force to the mantle  34  preventing further relative rotation. 
     Head nut  52  includes an internal threaded face  60  engaging the threaded bearing sleeve  32 . An external face  62  is substantially parallel and coaxial to the threaded face  60 . A lower face  64  is perpendicular and coaxial to the threaded face  60  extending between the threaded face  60  and the external face  62 . An upper face  66  is parallel to the lower face  64  and perpendicular and coaxial to the threaded face  60 , extending between the threaded face  60  and the external face  62 . In one embodiment of the invention, the head nut  52  has an outer diameter of approximately twenty-nine inches, an inner diameter of approximately twenty-four inches and a height of approximately five inches. Head nut bores  68 A and  68 B extend perpendicularly into the lower face  64 , and are disposed at diametrically opposite points of the lower face  62  (for example at noon and six o&#39;clock as on the face of a clock). In one embodiment, each bore  68 A and  68 B has a diameter of approximately one inch and a depth of approximately three quarters of an inch. 
     Burning ring  54  includes a top face  70 , an outer face  72 , an inner face  74  and a bottom face  76 . The top face  70  of the burning ring  54  contiguously engages the lower face  64  of the head nut  52 . The bottom face  76  is parallel and coaxial to the top face  70  and includes a raised lip  77  which engages and centers the mantle  34  about the shaft  18 . The outer face  72  is perpendicular and coaxial to the top face  70  and extends between the top face  70  and the bottom face  76 . The inner face  74  is parallel to the outer face  72  and extends between the top face  70  and the bottom face  76 . In one embodiment, the outer diameter of the burning ring  54  is approximately twenty-nine inches, and the inner diameter is approximately twenty-five inches. Burning ring bores (or apertures)  78 A and  78 B extend perpendicularly into top face  70  through the burning ring  54  and out the bottom face  76 . Each burning ring bore  78 A and  78 B includes an inner wall  79 A and  79 B and is disposed directly below the head nut bores  68 A and  68 B respectively. Although dimensions have been provided for one embodiment of the inventive head nut assembly  50 , a person skilled in the art would realize that dimensions will vary according to the size of the gyratory crusher  10 . 
     The dowel shaped keys  56 A and  56 B are disposed in the burning ring bores  78 A and  78 B and extend upwardly into the head nut bores  68 A and  68 B. The keys  56 A and  56 B are typically welded into the burning ring bores  78 A and  78 B (preferably by fillet welding the bottom of each key  56 A and  56 B to the inner wall  79 A and  79 B of the burning ring bores  78 A and  78 B proximate to the bottom face  76  of the burning ring). Thus, the keys  56 A and  56 B are completely captured inside the head nut  52  and the burning ring  54 , with no part of either key  56 A and  56 B exposed to the crushing chamber  36 . 
     Capturing the keys  56 A and  56 B entirely within the head nut assembly  50  prevents the keys  56 A and  56 B from being subject to impingement of the crushing material. This prevents the keys  56 A and  56 B from being knocked out of bores  68 A,  68 B,  78 A, and  78 B which would allow the head nut  52  to rotate independently from the burning ring  54  causing the problems described above. Additionally, the use of the dowels  56 A and  56 B to key the head nut  52  to the burning ring  54  prevents the need to weld to the head nut  52 . Welding to the head nut  52  can distort the head nut  52  requiring the head nut  52  to be cut off when it is to be removed, possibly damaging the threaded shoulder  44  of the bearing sleeve  32  in the process. Damage to the head nut  52  can thereby result in a great expense and associated downtime while the head nut  52 , bearing sleeve  32  and possibly the shaft  18  are repaired. 
     The bottom face  76  of the burning ring  54  is generally contiguous with an upper surface  80  of the mantle  34 . Mantle upper surface  80  is typically wider than the bottom face  76  of the burning ring  54  so as to form a shoulder  82  with the burning ring outer face  72 . Preferably, a fillet weld  84  is used to attach the burning ring  54  to the mantle  34  along the shoulder  82 . Welding the ring  54  to the mantle  34  connects the mantle  34  to the head nut assembly  50  during operation of the crusher  10 . Since the burning ring  54  will be cut off during change out of the mantle  34 , distortion due to welding is not a concern. Welding the burning ring  54  is a more reliable method of securing the ring  54  to the mantle  34  than using a keying method since it eliminates any possibility of keys coming loose and allowing the ring  54  to rotate relative to the mantle  34 . Additionally, welding the ring  54  to the mantle  34  has the advantage of allowing the head nut assembly  50  to be tightened onto the mantle  34  without the necessity of aligning grooves or slots for keys. The head nut assembly  50  is fully torqued onto the mantle  34  and the ring  54  is fillet welded to the mantle  34 . Although the preferred embodiment of the invention welds the mantle  34  to the burning ring  54 , a person skilled in the art would realize that the mantle  34  can be keyed to the burning ring  54 . 
     The inventive head nut assembly  50  has the additional advantage of being easily manufactured and installed in the crusher  10 . The only machining required on the head nut  52  and the burning ring  54  for the keying system are the bores  68 A,  68 B,  78 A and  78 B which are easily machined using a drill-press. The dowels  56 A and  56 B do not need to be press fitted into the bores  68 A,  68 B,  78 A and  78 B in order to maintain a secure connection between the head nut  52  and the burning ring  54 , since they can be welded to the inner walls  79 A and  79 B of the burning ring bores  78 A and  78 B. Thus, standard machining tolerances can be used. 
     The exploded view shown in FIG. 4 illustrates the method used to install the head nut assembly  50 . The mantle  34  is set on the main shaft  18  and shimmed into position. The keys  56 A and  56 B are disposed into bores  68 A,  68 B,  78 A and  78 B. For convenience, the head nut  52  and the burning ring  54  can be lightly tack welded together (although this is not necessary). Tack welding the head nut  52  does not distort the nut  52  since heat is only applied to the nut  52  for a short amount of time. The keys  56 A and  56 B are fillet welded to the inner walls  79 A and  79 B of the burning ring bores  78 A and  78 B. The assembly of the head nut assembly may occur where it is manufactured (i.e. a burning ring assembly including the keys  56 A and  56 B welded in place and, if desired, the head nut  52  and burning ring  54  back welded together), limiting the amount of work that needs to be done at the crusher  10  site (eliminating crusher downtime). A person skilled in the art would realize, however, that the head nut assembly may take place at the crusher location. 
     The head nut assembly  50  is screwed onto the main shaft  18  until the raised lip  77  on the bottom face  76  of the burning ring  54  engages the inner diameter of the mantle  34 . The lip  77  acts to center the mantle  34  about the main shaft  18  as the head nut assembly  50  is tightened onto the mantle  34 . The backing material  38  is poured and allowed to harden and the burning ring  54  is fillet welded to the mantle  34 . 
     When the mantle  34  is worn out and needs to be replaced, the burning ring  54  is cut horizontally (i.e. with a plasma torch), relieving pressure against the head nut  52  and allowing it to be unscrewed and re-used. The old mantle is removed and a new mantle is positioned about the shaft  18 . The above process is then repeated using a new burning ring attached to the head nut  52  with new keys. 
     The preferred embodiment of the invention secures the keys  56 A and  56 B into the burning ring  54  bores  78 A and  78 B by welding them to the inner wall  79 A and  79 B. Welding has the advantage of fixing the keys  56 A and  56 B into place, eliminating tipping of the keys  56 A and  56 B inside the bores  68 A,  68 B,  78 A, and  78 B. Tipping of the keys  56 A and  56 B causes greater shear forces on the keys  56 A and  56 B increasing the possibility of key breakage and separation of the nut  52  from the ring  54 . An alternate embodiment of the invention would place keys  156 A and  156 B in blind bores  168 A,  168 B,  178 A, and  178 B drilled into the burning ring  54 , as shown in FIG.  5 . The keys  156 A and  156 B may be press fit into the bores  178 A and  178 B to eliminate tipping of the keys  156 A and  156 B. An additional alternative configuration would utilize head nut bores  180 A and  180 B which extend completely through the head nut  52 , and blind burning ring bores  182 A and  182 B in the burning ring  54 , as shown in FIG.  5 A. The keys  156 A and  156 B are captured in bores  180 A,  180 B,  182 A and  182 B. The keys  156 A and  156 B are then fillet welded into the head nut bores  180 A and  180 B (once again, the short welding time to weld the two keys  156 A and  156 B to the head nut  52  does not cause head nut  52  distortion). Still another alternate embodiment is to insert threaded keys  190 A and  190 B into threaded burning ring bores  192 A and  192 B disposed in the burning ring  54  as shown in FIG.  5 B. The threaded keys  190 A and  190 B eliminate tipping of the keys  190 A and  190 B in the burning ring bores  192 A and  192 B. The upper end of the keys  190 A and  190 B extend into blind head nut bores  194 A and  194 B, disposed in the head nut  52 , locking the head nut  52  rotationally with respect to the burning ring  54 . 
     Although the preferred embodiment uses two keys to connect the burning ring  54  to the head nut  52 , a person skilled in the are would realized that additional keys may be used, as shown in FIG.  6 . Keys  256 A,  256 B,  256 C and  256 D are positioned between burning ring bores  278 A- 278 D and head nut bores  268 A- 268 D so that the keys  256 A- 256 D are not exposed to crushing material. Other key configurations utilizing additional keys spaced in various positions around the head nut assembly  50  may be used to secure the head nut  252  to the burning ring  254 . Additionally, a person skilled in the art would realize that other key shapes may be utilized. For example, square, rectangular, or triangular pins may be used. 
     An additional advantage of the inventive head nut assembly  50  is the use of captured keys  56 A and  56 B inside the head nut  52  as an indication of head nut  52  wear. Although the head nut  52  does not wear as quickly as the mantle  34 , eventually the head nut  52  does need to be replaced. An easy method for the operator to determine when this change-out needs to take place is when the keys  56 A and  56 B begin to show through the external face  62  of the head nut  52 , as shown in FIG.  7 . 
     The innovative method of positioning the keys  56 A and  56 B in a captured position between the head nut  52  and the burning ring  54  serves to maintain a reliable connection in the head nut assembly  50 . Repair and down time costs are thereby substantially reduced, and maintenance is more easily scheduled and performed. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.