Abstrict 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.
Claims What is claimed is:
1. A head nut assembly for a gyratory crusher, the crusher including
a shaft having a lower portion, a tapered middle portion and a threaded
upper portion extending above the tapered portion and a mantle encompassing
the tapered middle portion having a correspondingly tapered internal
side and an upper side wherein the internal side is in generally
continuous supportive engagement with the shaft middle portion,
comprising:
a head nut threadably secured to the upper portion of the shaft,
having a lower face, wherein at least one bore extends vertically
upward into the lower face;
an annular ring disposed around the shaft between the mantle and
the head nut, the ring having a lower surface secured to the upper
side of the mantle so as to prevent relative rotational movement
between the mantle and the ring, and an upper surface wherein the
upper surface is contiguous with the lower face; and
at least one key disposed between the head nut and the annular
ring so as to rotationally couple the head nut to the annular ring,
wherein the key is completely captured inside the head nut and annular
ring.
2. The apparatus of claim 1 wherein the key is welded to the annular
ring.
3. The apparatus of claim 2 wherein the annular ring lower surface
is welded to the upper surface of the mantle.
4. The apparatus of claim 3 wherein the key is in the shape of
a dowel.
5. The apparatus of claim 1 wherein the annular ring further comprises:
at least one aperture extending downwardly into the upper surface,
wherein the key is disposed in the aperture, extending upwardly
into the head nut bore, so as to completely capture the key inside
the bore and aperture.
6. The apparatus of claim 5 wherein the annular ring lower surface
is welded to the upper side of the mantle.
7. The apparatus of claim 6 wherein the key is in the shape of
a dowel.
8. The apparatus of claim 1 wherein the annular ring further comprises
at least one aperture having an internal wall, extending downwardly
into the upper surface, extending through the annular ring to the
lower surface, wherein the key is disposed in the aperture extending
upwardly into the head nut bore.
9. The apparatus of claim 8 where the key is welded to the internal
wall of the aperture.
10. The apparatus of claim 9 where the annular ring lower surface
is welded to the upper side of the mantle.
11. The apparatus of claim 10 wherein the key is in the shape of
a dowel.
12. A head nut assembly for a gyratory crusher comprising:
a head nut having a lower face and a bore extending perpendicularly
into the lower face;
a burning ring having an upper side and an aperture extending perpendicularly
into the upper side, wherein the upper side is contiguous with the
lower face; and
a key disposed within the aperture and extending into the bore,
wherein the key is completely captured within the head nut and the
burning ring.
13. The head nut assembly of claim 12 wherein the burning ring
further comprises:
a lower side, wherein the aperture extends through the burning
ring to the lower side, and the key is welded to the burning ring.
14. The head nut assembly of claim 13 wherein the key is dowel
shaped.
15. A burning ring for use with a head nut in a gyratory crusher,
the head nut having a lower face and a bore extending perpendicularly
into the lower face, the burning ring comprising:
a lower surface and an upper surface, wherein the upper surface
is contiguous with the lower face;
an aperture extending perpendicularly into the upper surface through
the burning ring, and out the lower surface; and
a key having a first end for positioning in the aperture and a
second end for extending upwardly into the bore so that when the
burning ring is positioned adjacent the head nut the key is completely
captured inside the aperture and the bore and acts to couple the
ring to the head nut.
Description 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 head nut assembly for a gyratory crusher machine.
The head nut assembly includes a head nut and a burning ring coupled
together using a key system. The head nut assembly is threaded onto
a shaft and is tightened to hold a mantle in place on the shaft
In particular, the burning ring portion of the assembly is welded
to the mantle of the crusher. The head nut and burning ring are
connected by dowels disposed between the contiguous surfaces of
the head nut and the burning ring. The dowel is entirely captured
inside the burning ring and the head nut. When the burning ring
is cut, the head nut is able to freely turn in relation to the mantle.
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 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 56A and 56B. 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 68A and 68B 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'clock as on the face of a clock). In one embodiment, each bore
68A and 68B 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) 78A and 78B extend perpendicularly
into top face 70 through the burning ring 54 and out the bottom
face 76. Each burning ring bore 78A and 78B includes an inner wall
79A and 79B and is disposed directly below the head nut bores 68A
and 68B 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 56A and 56B are disposed in the burning ring
bores 78A and 78B and extend upwardly into the head nut bores 68A
and 68B. The keys 56A and 56B are typically welded into the burning
ring bores 78A and 78B (preferably by fillet welding the bottom
of each key 56A and 56B to the inner wall 79A and 79B of the burning
ring bores 78A and 78B proximate to the bottom face 76 of the burning
ring). Thus, the keys 56A and 56B are completely captured inside
the head nut 52 and the burning ring 54 with no part of either
key 56A and 56B exposed to the crushing chamber 36.
Capturing the keys 56A and 56B entirely within the head nut assembly
50 prevents the keys 56A and 56B from being subject to impingement
of the crushing material. This prevents the keys 56A and 56B from
being knocked out of bores 68A, 68B, 78A, and 78B 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 56A and 56B 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 68A, 68B, 78A and 78B which
are easily machined using a drill-press. The dowels 56A and 56B
do not need to be press fitted into the bores 68A, 68B, 78A and
78B 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 79A and 79B of the burning ring bores 78A and 78B. 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 56A and 56B are disposed
into bores 68A, 68B, 78A and 78B. 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 56A and 56B are fillet welded to the inner
walls 79A and 79B of the burning ring bores 78A and 78B. The assembly
of the head nut assembly may occur where it is manufactured (i.e.
a burning ring assembly including the keys 56A and 56B 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 56A
and 56B into the burning ring 54 bores 78A and 78B by welding them
to the inner wall 79A and 79B. Welding has the advantage of fixing
the keys 56A and 56B into place, eliminating tipping of the keys
56A and 56B inside the bores 68A, 68B, 78A, and 78B. Tipping of
the keys 56A and 56B causes greater shear forces on the keys 56A
and 56B 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 156A and 156B in blind bores 168A, 168B, 178A,
and 178B drilled into the burning ring 54 as shown in FIG. 5. The
keys 156A and 156B may be press fit into the bores 178A and 178B
to eliminate tipping of the keys 156A and 156B. An additional alternative
configuration would utilize head nut bores 180A and 180B which extend
completely through the head nut 52 and blind burning ring bores
182A and 182B in the burning ring 54 as shown in FIG. 5A. The keys
156A and 156B are captured in bores 180A, 180B, 182A and 182B. The
keys 156A and 156B are then fillet welded into the head nut bores
180A and 180B (once again, the short welding time to weld the two
keys 156A and 156B to the head nut 52 does not cause head nut 52
distortion). Still another alternate embodiment is to insert threaded
keys 190A and 190B into threaded burning ring bores 192A and 192B
disposed in the burning ring 54 as shown in FIG. 5B. The threaded
keys 190A and 190B eliminate tipping of the keys 190A and 190B in
the burning ring bores 192A and 192B. The upper end of the keys
190A and 190B extend into blind head nut bores 194A and 194B, 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 256A, 256B, 256C and 256D are positioned between burning
ring bores 278A-278D and head nut bores 268A-268D so that the keys
256A-256D 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 56A and 56B 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 56A and
56B 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 56A and 56B 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. |