Note: Descriptions are shown in the official language in which they were submitted.
CA 02656567 2009-06-11
CUTTINGS REMOVAL WIPERS FOR CUTTER ASSEMBLIES AND
METHOD
I. Field of the Invention
This invention generally relates to cutter assemblies including mechanisms for
excluding or keeping debris and other formation particles away from bearings
of the
assemblies during earth boring.
2. Background of the Invention
Earth boring cutter assemblies have cutting heads with cutter shells that are
rotatably supported on journals for rotation during boring operations. Due to
the
abrasive environment at a rock face being drilled and the confined volume in
which
the cuttings and other debris are held in close proximity to the cutter heads,
entry of
the cuttings and debris into the bearings of the cutter heads has been a
problem that
several have attempted to address in a variety of ways. In some instances,
seals
including o-rings and/or other ring-type seals have been incorporated to form
a barrier
between an interior and an exterior of the cutter heads. Bearings are held
between
bearing surfaces on respective cutter shells and journals of the cutter heads
in an
interior of the cutter heads and are protected from the abrasive environment
on an
exterior by the seals. However, the cuttings and debris still tend to enter
the seals and
reduce the rotational movement that these seals are intended to permit. The
cuttings
and debris can also damage or interfere with the seals so that the cuttings
and debris
can get into the bearings of the cutter heads and inhibit the rotational
movement
and/or damage the bearings.
In a specific example, a seal for a replaceable cutter that is used in the
raise
= boring industry may typically be a mechanical face seal. As used in this
industry, the
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mechanical face seal is incorporated to seal the bearing lubricant in and
exclude
formation particles, which may include the cuttings and other debris. The face
seal
assembly is comprised of two metal seal rings and two o-rings forming two sets
of a
seal ring and an o-ring. The seal sets are assembled against each other, with
the two
seal rings each having a very flat dynamic seal surface. The o-ring provides
and
maintains a preload to the seal ring. It has been found, however, that
contaminants
produced during operation pack into the area adjacent to the seal rings and
have the
net effect of reducing the life of the seal.
SUMMARY OF THE INVENTION
There is a need for a device that sweeps cuttings and other debris away from
the seals and bearings of cutter assemblies. The present invention generally
relates to
cutter assemblies which include mechanisms for removing debris during earth
boring.
More specifically, the subject invention is a cutter assembly for raise boring
and other
applications in which the cutter assembly has wipers on radially facing
dynamic
interface surfaces for sweeping cuttings away from seals and bearings of the
assembly
during earth boring.
In a simple form, one embodiment of the present invention may include a
replaceable cutter assembly having a journal with at least one journal bearing
surface
and at least one radially outwardly facing dynamic journal interface surface.
The
cutter assembly may also have a cutter shell rotatably supported on the
journal. The
cutter shell may have a cutter shell bearing surface and at least one radially
inwardly
facing dynamic cutter shell interface surface. The cutter assembly may further
include
at least one wiper on the at least one of the interface surfaces of one of the
journal and
the cutter shell. The at least one wiper may thus be proximate to and face the
at least
one of the interface surfaces of the other of the journal and the cutter
shell.
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The wiper may be a low profile lug integrally formed on one of the journal and
the cutter shell. A rotational axis of the cutter shell on the journal defines
an axial
direction. The wiper may have an edge that extends generally diagonally
relative to
the axial direction. Alternatively, the wiper may have an edge that extends
generally
helically relative to the axial direction.
The replaceable cutter assembly may have a plurality of wipers including the
at least one wiper. The wipers may protrude radially from the at least one of
the
interface surfaces. The plurality of wipers may include four permanent low
profile
lugs circumferentially spaced from each other on the at least one of the
dynamic
journal interface surfaces relative to the rotational axis. The permanent low
profile
lugs further may have edges that extend generally diagonally relative to the
axial
direction.
The replaceable cutter assembly may further include at least one seal
sealingly
contacting the cutter shell and the cutter journal between the dynamic
interface
surfaces of the cutter shell and the cutter journal on one axial side and the
bearing
surfaces of the cutter shell and the cutter journal on another axial side of
the at least
one seal.
The replaceable cutter assembly may include a plurality of radially outwardly
facing dynamic journal interface surfaces including the at least one radially
outwardly
facing dynamic journal interface surface. The replaceable cutter assembly may
also
include a plurality of radially inwardly facing dynamic cutter shell interface
surfaces
including the at least one radially inwardly facing dynamic cutter shell
interface
surface. The plurality of radially inwardly facing dynamic cutter shell
interface
surfaces may form respective pairs of interface surfaces with the plurality of
radially
outwardly facing dynamic journal interface surfaces. The assembly may have at
least
one of the wipers on at least one of the interface surfaces of each of the
pairs of
interface surfaces. Each of the at least one of the wipers may be proximate to
and face
the other of the interface surfaces of each of the pairs of the interface
surfaces.
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The present invention is believed to have patentable elements that are not
limited to the entire assembly. As one example, the invention may encompass a
replaceable cutter journal that may include a journal having at least one
journal
bearing surface and at least one radially outwardly facing dynamic journal
interface
surface. The cutter journal may have at least one wiper on the at least one
interface
surface.
The radially outwardly facing dynamic journal interface surface may have at
least one first portion with a first diameter. The radially outwardly facing
dynamic
journal interface surface may have at least one second raised portion with a
second
diameter greater than the first diameter. The first and second portions may
extend
along a common circumferential line.
In the replaceable cutter journal, a rotational axis of the journal may define
an
axial direction. The radially outwardly facing dynamic journal interface
surface may
extend circumferentially and may be spaced proximally relative to the journal
bearing
surface in the axial direction.
The wiper may have an edge that extends generally diagonally relative to the
axial direction. The replaceable cutter journal may have a plurality of wipers
including the at least one wiper. The wipers may form second portions of the
radially
outwardly facing dynamic journal interface surface. The wipers may protrude
radially
from first portions of the at least one interface surface. The plurality of
wipers may
include four permanent low profile lugs circumferentially spaced from each
other on
the dynamic journal interface surface relative to the rotational axis. The
permanent
low profile lugs may have edges that extend generally diagonally relative to
the axial
direction.
The at least one second portion of the radially outwardly facing dynamic
journal interface surface may include the at least one wiper integrally formed
as one
piece with the first portion of the radially outwardly facing dynamic journal
interface
surface.
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=
The dynamic journal interface surface may be on a separable piece removably
attached to the journal. The separable piece may have a seal retainer.
The replaceable cutter journal may include a plurality of radially outwardly
facing dynamic journal interface surfaces including the at least one radially
outwardly
facing dynamic journal interface surface. Each of the radially outwardly
facing
dynamic journal interface surfaces may be on a separable piece removably
attached to
the rest of the journal.
In another aspect or embodiment, the present invention may encompass a
replaceable cutter shell having at least one cutter shell bearing surface and
at least one
radially inwardly facing dynamic cutter shell interface surface. The
replaceable cutter
shell may also include at least one wiper on the at least one interface
surface.
The radially inwardly facing dynamic cutter shell interface surface may have
at
least one first portion having a first diameter and at least one second raised
portion
having a second diameter less than the first diameter. The first and second
portions
may extend along a common circumferential line.
A rotational axis of the cutter shell may define an axial direction. The
radially
inwardly facing dynamic journal interface surface may extend circumferentially
and
may be spaced proximally relative to the cutter shell bearing surface in the
axial
direction.
The wiper may have an edge that extends generally diagonally relative to the
axial direction. The replaceable cutter shell may include a plurality of
wipers
including the at least one wiper. The wipers may form second portions of the
radially
inwardly facing dynamic cutter shell interface surface. The wipers may
protrude
radially from first portions of the at least one interface surface. The
plurality of
wipers may include four permanent low profile lugs circumferentially spaced
from
each other on the dynamic cutter shell interface surface relative to the
rotational axis.
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The permanent low profile lugs may have edges that extend generally diagonally
relative to the axial direction.
At least one second portion of the radially inwardly facing dynamic journal
interface surface may include the at least one wiper integrally fowled as one
piece
with the first portion of the radially inwardly facing dynamic journal
interface surface.
In another aspect of the invention, a separate piece may be removably
attachable to at least one of a cutter assembly journal or to a cutter
assembly cutter
shell. The separate piece may include a radially facing dynamic interface
surface that
may have at least a first portion and a second portion. The first and second
portions
may have respective first and second diameters different from each other. The
first
and second portions may extend along a common circumferential line. At least
one of
the first and second portions may form low profile lugs relative to the other
of the first
and second portions. The separate piece may have attachment structure for
removably attaching the piece to at least one of the cutter assembly journal
and the
cutter assembly cutter shell. The separate piece may include a seal retainer
with a seal
retaining structure.
In another aspect, the present invention may include a method of inhibiting
entry of debris into a cutter assembly. The method may include sweeping a
first
radially facing dynamic interface surface with at least one wiper disposed on
a second
oppositely radially facing dynamic interface surface. The method may also
include
moving debris axially away from at least one seal and at least one bearing of
the cutter
assembly. The steps of sweeping and moving may include automatically sweeping
and moving during regular rotation of a cutter shell of the cutter assembly
relative to a
cutter journal of the cutter assembly. The steps of sweeping and moving may
include
presenting a leading edge of the at least one wiper transverse to an axial
direction
defined by an axis of rotation of the cutter shell relative to the cutter
journal. The
steps of sweeping and moving may include moving the leading edge of the at
least one
wiper circumferentially along the second oppositely radially facing dynamic
interface
surface.
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The method may include sweeping a plurality of radially facing dynamic
interface surfaces including the first radially facing dynamic interface
surface with
a plurality of wipers including the at least one wiper. The plurality of
wipers may
be disposed on a plurality of oppositely facing dynamic interface surfaces
including the second oppositely radially facing dynamic interface surface. The
method may include moving debris axially away from a plurality of seals
including the at least one seal and moving debris axially away from a
plurality of
bearings including the at least one bearing of the cutter assembly. The steps
of
sweeping and moving may include automatically sweeping and moving during
regular rotation of the cutter shell of the cutter assembly relative to the
cutter
journal of the cutter assembly.
According to another aspect of the present invention, there is provided a
replaceable cutter assembly, comprising:
a journal having at least one journal bearing surface, the journal having at
least one radially outwardly facing dynamic journal interface surface;
a cutter shell rotatably supported on the journal, the cutter shell having a
cutter shell bearing surface and the cutter shell having at least one radially
inwardly facing dynamic cutter shell interface surface;
a plurality of wipers, wherein the wipers protrude radially from the at least
one of the interface surfaces of one of the journal and the cutter shell, and
wherein
at least one one of the wipers is proximate to and faces the at least one of
the
interface surfaces of the other of the journal and the cutter shell; and
wherein a rotational axis of the cutter shell defines an axial direction, the
plurality of wipers comprises four permanent low profile lugs
circumferentially
spaced from each other on the at least one of the dynamic journal interface
surfaces
relative to the rotational axis, wherein the permanent low profile lugs
further
comprise edges that extend generally diagonally relative to the axial
direction.
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According to another aspect of the present invention, there is provided a
replaceable cutter assembly, comprising:
a journal having at least one journal bearing surface and at least one
radially outwardly facing dynamic journal interface surface;
a plurality of wipers, wherein the wipers form second portions of the
radially outwardly facing dynamic journal interface surface and the wipers
protrude radially from first portions of the at least one interface surface;
wherein a rotational axis of the cutter shell defines an axial direction, the
plurality of wipers comprises four permanent low profile lugs
circumferentially
spaced from each other on the dynamic journal interface surface relative to
the
rotational axis, wherein the permanent low profile lugs further comprise edges
that
extend generally diagonally relative to the axial direction.
According to another aspect of the present invention, there is provided a
cutter assembly, comprising:
a journal;
a cutter shell rotatably mounted to the journal, the cutter shell having
opposed first and second openings;
wherein the journal extends through the opposed first and second openings;
and
a first wiper positioned to remove debris from between the journal and
cutter shell proximate to the first opening.
According to another aspect of the present invention, there is provided a
cutter assembly, comprising:
a journal;
a cutter shell rotatably mounted to the journal, the cutter shell having
opposed first and second openings;
wherein the journal extends through the opposed first and second openings;
a first wiper positioned to remove debris proximate to the first opening
from between the journal and cutter shell; and
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,
a second wiper positioned to remove debris proximate to the second
opening from between the journal and cutter shell.
According to another aspect of the present invention, there is provided a
cutter assembly, comprising:
a journal;
a cutter shell rotatably mounted to the journal, the cutter shell having
opposed first and second openings;
wherein the journal extends through the opposed first and second openings;
a first seal positioned proximate to the first opening of the cutter shell;
a first wiper positioned to remove debris from between the journal and
cutter shell, and away from the first seal;
a second seal positioned proximate to the second opening of the cutter
shell; and
a second wiper positioned to remove debris from between the journal and
cutter shell, and away from the second seal.
The foregoing and other features and advantages of the present invention will
be apparent from the following more detailed description of the particular
embodiments of the invention, as illustrated in the accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
FIG. lA is a perspective view of a journal 'having wipers according to an
embodiment of the present invention;
FIG. 1B is a sectional view at a central plane coincident with a rotational
axis
of a cutter assembly including a journal similar to the journal of Figure lA
according
to an embodiment of the present invention;
FIG. 2 is a partial sectional view similar to Figure 1B showing a side view of
the journal having wipers according to an embodiment of the present invention;
FIG. 3 is a detailed view of an area In of Figure 1B showing details of an
alternative embodiment according to the present invention; and
FIG. 4 is a detailed view of an area IV of Figure 1B showing details of an
alternative embodiment according to the present invention.
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DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
As discussed above, embodiments of the present invention relate generally to
cutter assemblies including mechanisms for excluding debris during earth
boring.
Seals of a variety of types and configurations are known. For example, U.S.
Patent No. 5,984,024 to Strand, is an example of a raise boring cutter
assembly that
uses a mechanical seal. U.S. Patent No. 6,033,117 to Cariveau et al., also
includes a
large variety of seal configurations that may additionally or alternatively be
incorporated together with various cutter assemblies. While the present
invention may
be particularly useful in raise boring applications due to the relatively
smaller amount
of fluids utilized in cleaning and removing cuttings, it is to be understood
that the
teachings of this invention may be equally applied to other earth boring
applications
including those that incorporate pressurized fluids in cleaning and removing
of
cuttings.
Figure IA is a perspective view of a journal 12 for a cutter assembly 13,
(shown in Figure 1B and 2), for earth boring applications. The journal 12 may
have
wipers 15 in the form of low profile lugs or raised portions on a first
radially
outwardly facing dynamic journal interface surface 18. The dynamic journal
interface
surface 18 may have at least one first portion 21 and at least one second
portion 24.
The journal 12 has one or more bearing surfaces 27, 30, 33, and a second
radially
outwardly facing dynamic journal interface surface 36. The second radially
outwardly
facing dynamic journal interface surface 36 may have wipers 39, at least one
first
portion 42, and at least one second portion 45 similar to the first radially
outwardly
facing dynamic journal interface surface 18. The journal 12 may be supported
together with the rest of the cutter assembly 13 in a saddle. U.S. Patent No.
5,984,024
to Strand shows and describes a number of saddle configurations.
As shown in the sectional view of Figure 1B, the wipers 15, 39 may be
disposed on the cutter journal 12, as shown in Figure IA, or alternatively on
a cutter
shell 16, as shown in dashed lines in Figure 1B. The wipers 15, 39 are in the
form of
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low profile lugs that are angled relative to an axis of rotation and central
axis 48 of a
cutter head shell 16 and cutter journal 12, respectively. The low profile lugs
or wipers
15, 39 are shown on the dynamic interface surfaces 18, 36 between the cutter
head
cutter shell 16 and the cutter journal 12 and may be integral with either the
cutter
journal 12. Alternatively, the low profile lugs or wipers 15, 39 may be on an
oppositely facing dynamic interface surface of the cutter shell 16. The low
profile
lugs or wipers 15, 39 are located exteriorly and adjacent to respective seals
51, 54 of
the cutter shell 16. The lugs or wipers 15, 39 are angled so that relative
motion
between the cutter journal 15 and the cutter shell 16 sweeps debris axially
out from
between the journal 15 and the shell 16. The lugs or wipers 15, 39 are
oriented to
move formation particles including cuttings and other debris axially away from
the
seal as the cutter shell 16 rotates relative to the cutter journal 15 during
use. In this
way, the wipers 15, 39 also move the debris away from one or more bearings 57,
58,
59 and respective bearing surfaces 27, 30, 33, 61, 62, 63 in an interior of
the cutter
assembly 13.
As may be appreciated from the partial sectional view of Figure 2, a wiper 15,
39 may be formed on a dynamic interface surface 18, 36 of the journal 12
between a
stationary component (journal 12) and a rotating component (cutter shell 16).
The
wiper 15, 39 is angled from the axis of rotation 48 of the two components in
such a
way that when the cutter shell is rotating in the normal "drilling" direction
shown by
arrow 66 in Figure 2, the formation particles including cuttings and other
debris are
swept out of the dynamic interface. Removing debris from the dynamic interface
in
this way keeps the area adjacent to the cutter seals 51, 54 much more clean
and
provides extended seal life. The wiper(s) can be formed by welding, machining,
or
other suitable methods.
The wipers 15 have leading edges 69 and the wipers 39 have leading edges 72
that confront the formation particles that are brought into contact therewith
at least in
part by the cutter shell and forces them out from between the cutter journal
15 and the
cutter shell 16 in opposite directions as shown by arrows 75, 78. To this end,
the
leading edge, and the wipers 15, 39 in general, may be oriented at angles 81,
84 from
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approximately ten degrees to approximately eighty degrees relative to the axis
of
rotation 48 or axial direction as shown. Alternatively, the angles 81, 84 may
be in a
range from approximately thirty to forty-five degrees inclusive. The angles
may be
inside or outside these ranges as long as they provide the function of moving
the
formation particles away from the seals 51, 54. As may be appreciated, if the
wipers
are supported on the cutter shell 16 and the direction of rotation 66 of the
cutter shell
16 is the same, then the angle of the leading edges of the wipers 15, 39 will
need to be
slanted oppositely to those shown on the journal 12 in Figure 2 in order to
sweep the
formation particles out from between the cutter shell 16 and the cutter
journal 15.
Referring back to Figure 1B, the heights 87, 88 of the wipers 15, 39 may be in
a range from approximately one thirty-second of an inch to approximately one-
half
inch depending on an overall size of the cutter head and other factors. The
heights 87,
88 may be approximately three sixteenths of an inch. These heights may be
expressed
as radial or diametric differences between the second portions 24, 45 and the
first
portions 21, 42 of the radially outwardly facing dynamic interface surfaces as
shown
and described with regard to Figure 1A. An alternative expression of the
heights may
be that the heights 87, 88 may be from approximately one tenth to
approximately five
times a width 91 of the wipers 15, 39. Although the drawing figures are not
necessarily to scale, it is to be understood that similar proportions may be
calculated
by measurements and comparisons of the actual drawing element in Figures 1A-4.
For example, the width of the wipers 15, 39 may be approximately one tenth the
diameter of the dynamic interface surfaces on which the wipers 15, 39 are
supported.
It is to be understood that the proportion of the second portion of the
dynamic surface
relative to the first portion should generally be small, the proportion of the
second and
first portions may be varied. For example, while only four relatively narrow
equally
spaced wipers 15, 39 are shown equally spaced on a circumference of the
dynamic
surfaces at each end of the cutter journal 12, wider wipers may be
incorporated. For
example, it is contemplated that the width 91 of a wiper 15, 39 could be as
much as
approximately one half the circumference of the dynamic surfaces on which the
wiper
15, 39 is supported.
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It is to be understood that the wipers 15, 39 may, in many if not most cases,
have the heights 87, 88 of a dimension smaller than regular clearances between
the
radially facing dynamic interface surfaces between the cutter assembly
journals and
cutter assembly cutter shells. Thus, customization of existing cutter
assemblies may
not be required other than steps to provide the wipers 15, 39 in accordance
with the
present invention.
For example, the first dynamic journal interface surface 18 shown in Figure 1
may be integral and form one piece with the rest of the cutter journal 12.
Thus, the
dynamic journal interface surface 18 may be machined together with the rest of
the
cutter journal 12 such as in a lathing process to integrally form the dynamic
journal
interface surface 18 at the larger diameter end of the journal 12 together
with the
bearing surfaces 27, 30, and 33. The wipers 15 may be added to a custom
machined
journal or may be added to a standard cutter journal such as by welding and
shaping
by a subsequent machining process, for example. Similarly, the radially
outwardly
facing dynamic journal interface surface 36 may be formed at the smaller
diameter
end of the journal 12. Alternatively, the interface surfaces may be formed on
radially
inwardly facing surfaces of the cutter shell. However, it is to be understood
that in
most cases on any given pair of mutually facing dynamic interface surfaces,
the wipers
may only be on one of the interface surfaces while the other of the surfaces
remains
smooth.
Figures 3 and 4 show detailed views of alternative embodiments of
corresponding regions 111 and IV of the sectional view of Figure 1A. As may be
appreciated, one or both of the dynamic interface surfaces may be added onto
the
cutter journal 12 and/or cutter shell 16. Figure 3 shows a sectional view of
the region
at the larger diameter end of the journal 12. Instead of the wiper 15 being
one piece
with the journal 12, the wiper is supported on a separable piece. While the
separable
piece may be any separable piece, Figure 3 shows the separable piece as a seal
retainer
101 that is held by attaching structure to the journal 12. The attaching
structure may
include a notch 104 and groove 107 in the journal 12 and a retaining ring 110
received
in the groove 107 and holding the retainer 101 in the notch 104. Additional
structure
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may include a slot on the retainer 101 and a dowel on the journal 12 and
engaging the
slot to inhibit rotation of the retainer 101 relative to the journal 12, for
example.
Alternatively or additionally, the attaching structure may be provided as a
threaded
connection between the separable piece and the journal. Further alternatively
or
additionally, the attaching structure may be provided by a slot and pin
combination.
As shown, the seal retainer 101 has a seal retaining structure that may
include
a generally reentrant o-ring and seal ring capture recess 113. Another o-ring
and seal
ring recess is formed between the journal 12 and the cutter shell 16. Thus, a
seal 117
having two seal rings 120 and two o-rings 123 may form a dynamic seal between
the
cutter journal 12 and the cutter shell 16. Advantageously, the seal retainer
may have
the dual function of retaining the seal 117 and supporting the wiper 15.
As shown in Figure 4, the wiper 39 may similarly be supported on a separable
piece. While the separable piece may be any separable piece such as any
annular
segment of the journal or shell, Figure 4 shows the separable piece as a seal
retainer
126 that is held by attaching structure to the journal 12. The attaching
structure may
include a notch 129 and groove 132 in the journal 12 and a retaining ring 135
received
in the groove 132 and holding the retainer126 in the notch 129. Alternatively
or
additionally, the attaching structure may be provided as a threaded connection
between the separable piece and the journal. Further alternatively or
additionally, the
attaching structure may be provided by a slot and pin combination. As shown
and
described with regard to Figure 3 above, the seal retainer 126 may have a seal
retaining structure that may include a generally reentrant o-ring and seal
ring capture
recess 138. Another o-ring and seal ring recess may be foimed between the
journal 12
and the cutter shell 16. Thus, a seal 141 having two seal rings 144 and two o-
rings
147 may form a dynamic seal between the cutter journal 12 and the cutter shell
16.
Advantageously, the seal retainer may have the dual function of retaining the
seal 141
and supporting the wiper 39.
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It is contemplated that the separable piece may be provided as a press-in ring
with wipers with or without seal retaining structure. This could be applied to
either or
both ends of the journal or the cutter shell as an annular segment.
Alternatively or
additionally, one or more separable pieces may have other configurations such
as
blocks having wipers or even as attachable wipers. The separable piece(s) may
be
attached to journals or cutter shells by one or more of set screws, pins,
welding,
tongue and groove structures enabling sliding in, or threads on the separable
piece
itself.
As described above, the wipers 15, 39 may be supported on either the journal
12 or on the cutter shell 16 as indicated by dashed lines in Figures 3 and 4.
Additionally, the wipers 15, 39 may be supported on separable pieces that may
be
attached to the cutter shell 16 instead of the cutter journal 12. Any
combination of
these teachings is within the spirit and scope of the present invention. One
configuration depicted in Figure lA may have a combination of a first seal
that may
be installed without a separable seal retainer on a larger diameter end of the
journal 12
and a second seal that may be installed and held in place by a separable seal
retainer
like that shown and described with regard to Figure 4 on a smaller diameter
end of the
journal 12. Thus, the installation of the seals and bearings may be
facilitated.
It is to be understood that while the embodiments have been shown and
described as having dynamic interface surfaces that generally define straight
cylindrical surfaces that are parallel to the rotational axis 45 for each of
the journal
and the shell, and for the wipers 15, 39. That is, the interface surfaces are
shown as
being at a generally constant radius along their extent in a direction of the
rotational
axis 48, and the only differences in radii are between respective surfaces and
between
the surfaces and the wipers 15, 39. However, the dynamic interface surfaces
may be
angled relative to the rotational axis 48 in a range from approximately forty-
five
degrees radially inward toward the axis 48 from the inside of the shell 16
outward to
approximately forty-five degrees radially outward from the inside of the shell
16
outward. As shown in Figure 1B, the angles would more typically extend
radially
inward toward the axis 48 only slightly from the inside outward for ranges
150, 153
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from approximately ten degrees radially inward from an inside out to
approximately
thirty degrees radially outward from the inside out. Angles that correspond to
the
dynamic interface surfaces increasing in radius in a direction from the inside
outward
have the advantage of moving debris outward away from the seals 51 and 54 in a
path
of least resistance since the volume of space between the journal and the
shell
increases in an outward direction. Alternatively stated, incorporating
increasing radii
in outward directions of the shell and journal for the dynamic interface
surfaces
further inhibit packing of debris in an area near the seals 51 and 54. This
advantage
may be appreciated more when considering that the angles shown in two
dimensions
in Figure 1B really correspond to dynamic interface surfaces that are
generally
conically configured.
Solid arrow 156 represents a facing direction for a dynamic interface surface
of the journal 12 that has a decreasing radius in an inward direction relative
to the
shell 16 and journal 12. Solid arrow 159 represents a facing direction for a
radially
outer surface of the wiper 39 on the dynamic interface surface with the facing
direction 156. At an opposite end of the range of angles shown for the dynamic
interface surfaces in Figure 1B, solid arrow 162 represents the facing
direction of the
dynamic interface surface of the journal 12 when the radius increases
inwardly. The
solid arrow 165 represents the facing direction for the radially outer surface
of the
wiper 39 on the dynamic interface surface with the facing direction 162. As
set forth
above, the corresponding dynamic interface surface on the shell would
generally
match in shape and be only slightly larger than the corresponding interface
surface and
wiper(s) of the journal for any angle within the range.
Dashed arrow 168 represents a facing direction for a dynamic interface surface
of the shell 16 that has a decreasing radius in an inward direction relative
to the shell
16 and journal 12. Dashed arrow 171 represents a facing direction for a
radially inner
surface of the wiper 39 as applied on the dynamic interface surface with the
facing
direction 168. At an opposite end of the range of angles shown for the dynamic
interface surfaces in Figure 1B, dashed arrow 174 represents the facing
direction of
the dynamic interface surface of the shell 12 when the radius increases
inwardly. The
= CA 02656567 2009-06-11
dashed arrow 177 represents the facing direction for the radially outer
surface of the
wiper 39 as applied on the dynamic interface surface with the facing direction
174.
As set forth above, the corresponding dynamic interface surface on the journal
12
would generally match in shape and be only slightly smaller than the
corresponding
interface surface and wiper(s) as applied to the shell 16 for any angle within
the range.
It is to be understood that the ranges of angles for the dynamic interface
surfaces relative to the rotational axis 48 described above may be applied to
both ends
of the journal 12 and shell 16 assembly. Furthermore, the ranges of angles may
be
applied to separable pieces that are coupled to one or both of the journal and
shell in
accordance with the embodiments shown in Figures 3 and 4.
The embodiments and examples set forth herein were presented in order to
best explain the present invention and its practical application and to
thereby enable
those of ordinary skill in the art to make and use the invention. However,
those of
ordinary skill in the art will recognize that the foregoing description and
examples
have been presented for the purposes of illustration and example only. The
description as set forth is not intended to be exhaustive or to limit the
invention to the
precise form disclosed. Many modifications and variations are possible in
light of the
teachings above without departing from the spirit and scope of the forthcoming
claims. For example, while the wipers have been shown and described as facing
radially, it is contemplated that a similar advantage may be achieved with
wipers that
face at an angle other than normal to a radial direction. Wipers on dynamic
interface
surfaces that face between zero and ninety degrees relative to a radial
direction are
considered to be within the scope of the present invention. The dynamic
inteiface
surfaces and/or the wipers are considered to be radially facing when there is
a radial
component to the direction in which they face.
16
