U.S. patent application number 15/501649 was filed with the patent office on 2017-08-17 for pick assembly, processing assembly comprising it, method of making it and method of using it.
This patent application is currently assigned to ELEMENT SIX GMBH. The applicant listed for this patent is ELEMENT SIX GMBH, ELEMENT SIX (UK) LIMITED. Invention is credited to PETER BUSH, DANIEL HLAWATSCHEK, BERND HEINRICH RIES, MARKUS KILIAN SCHARTING.
Application Number | 20170234128 15/501649 |
Document ID | / |
Family ID | 51662732 |
Filed Date | 2017-08-17 |
United States Patent
Application |
20170234128 |
Kind Code |
A1 |
RIES; BERND HEINRICH ; et
al. |
August 17, 2017 |
PICK ASSEMBLY, PROCESSING ASSEMBLY COMPRISING IT, METHOD OF MAKING
IT AND METHOD OF USING IT
Abstract
A pick assembly comprising a holder body, a strike body, a base
body attachable to a drive mechanism, and an interference assembly
comprising at least one interference member. The holder body
comprises a head portion and a shaft depending from the head
portion. The strike body comprises a super-hard strike tip. The
head portion and the strike body are cooperatively configured such
that the strike body can be attached to the head portion, the
strike tip being exposed for striking a body to be degraded when in
use. The base body comprises a base bore. The base bore, shaft and
interference assembly are cooperatively configured such that the
shaft can be secured within the base bore, the interference member
disposed between the shaft and the bore. Frictional interference
between the shaft, interference assembly and base bore is
sufficient to prevent rotation of the shaft within the base bore in
use.
Inventors: |
RIES; BERND HEINRICH;
(BURGHAUN, DE) ; HLAWATSCHEK; DANIEL; (BURGHAUN,
DE) ; SCHARTING; MARKUS KILIAN; (BURGHAUN, DE)
; BUSH; PETER; (DIDCOT, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELEMENT SIX GMBH
ELEMENT SIX (UK) LIMITED |
BURGHAUN
DIDCOT, OXFORDSHIRE |
|
DE
GB |
|
|
Assignee: |
ELEMENT SIX GMBH
BURGHAUN
DE
ELEMENT SIX (UK) LIMITED
DIDCOT, OXFORDSHIRE
GB
|
Family ID: |
51662732 |
Appl. No.: |
15/501649 |
Filed: |
August 10, 2015 |
PCT Filed: |
August 10, 2015 |
PCT NO: |
PCT/EP2015/068333 |
371 Date: |
February 3, 2017 |
Current U.S.
Class: |
299/10 |
Current CPC
Class: |
E21C 35/183 20130101;
E21C 35/1831 20200501; E21C 35/197 20130101; E21C 35/1835 20200501;
E21C 35/191 20200501; E01C 23/088 20130101; E01C 23/025
20130101 |
International
Class: |
E21C 35/197 20060101
E21C035/197; E01C 23/02 20060101 E01C023/02; E01C 23/088 20060101
E01C023/088; E21C 35/183 20060101 E21C035/183 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 20, 2014 |
GB |
1414831.6 |
Claims
1. A pick assembly comprising: a holder body, a strike body, a base
body attachable to a drive mechanism, and an interference assembly
comprising at least one interference member; in which: the holder
body comprises a head portion and a shaft depending from the head
portion, the strike body comprises a super-hard strike tip, the
head portion and the strike body are cooperatively configured such
that the strike body can be attached to the head portion, the base
body comprises a base bore; the base bore, shaft and interference
assembly being cooperatively configured such that the shaft can be
secured within the base bore, the interference member disposed
between the shaft and the bore, frictional interference between the
shaft, interference assembly and base bore being sufficient to
prevent rotation of the shaft within the base bore in use.
2. A pick assembly as claimed in claim 1, in which the combined
radial margin of interference between the shaft, the interference
member and the base bore is 10 to 200 microns.
3. A pick assembly as claimed in claim 1, in which the interference
member comprises a sleeve or ring configured to be capable of
accommodating the shaft.
4. (canceled)
5. (canceled)
6. (canceled)
7. A pick assembly as claimed in claim 1, in which the strike body
comprises polycrystalline diamond (PCD) material, or grains of
synthetic or natural diamond dispersed in a matrix comprising
carbide material.
8. (canceled)
9. (canceled)
10. A pick assembly as claimed in claim 1, in which the shaft is
coaxial with the strike body when the strike body is attached to
the holder body as for use.
11. A pick assembly as claimed in claim 1, in which the base bore
comprises a cylindrical inner surface and has a diameter of 18.00
to 21.00 millimetres (mm).
12. A pick assembly as claimed in claim 1, in which the base bore
comprises a cylindrical inner surface, at least an area of the side
of the shaft comprises a cylindrical surface, and the interference
member comprises a resilient sleeve configured to be capable of
accommodating the cylindrical area of the shaft and clamping it
with sufficient compressive force that the shaft will not rotate
relative to the sleeve in use, the thickness of the sleeve being
1.20 to 1.45 millimetres (mm).
13. A pick assembly as claimed in claim 1, in which at least a
portion of the shaft is cylindrical in shape and has a diameter of
16.00 to 19.00 millimetres (mm).
14. A pick assembly as claimed in claim 1, in which the
interference assembly comprises a spring sleeve and an interference
member located between the spring sleeve and the base bore when
assembled as for use.
15. A pick assembly as claimed in claim 1, in which the
interference member comprises elastomer material or other polymer
material.
16. A pick assembly as claimed in claim 1, in which the
interference assembly comprises a laterally extending portion that
will be located outside the base bore when assembled as for use,
and which will be capable of protecting the base body in use.
17. A pick assembly as claimed in claim 1, in which the
interference member is in the form of an O-ring or quad-ring.
18. A pick assembly as claimed in claim 1, in which the
interference assembly is configured such that a portion of the
shaft is spaced apart from the base bore, the portion and the base
bore not being connected by solid state material.
19. A pick assembly as claimed in claim 1, in which the
interference assembly is configured such that a volume between the
shaft and the base bore contains material from a body being
degraded by means of the pick.
20. (canceled)
21. A pick assembly as claimed in claim 1, in which the
interference assembly comprises a plurality of interference
members.
22. A processing assembly comprising a plurality of pick assemblies
as claimed in claim 1, attachable to a drive mechanism.
23. (canceled)
24. A processing assembly as claimed in claim 16, suitable for
pavement scarifying.
25. A processing assembly as claimed in claim 16, in which each of
the shafts of all of the pick assemblies have the same diameter and
the dimensions of the respective interference members differ from
each other to compensate for differences in at least one base bore
dimension.
26. (canceled)
27. (canceled)
28. A method of making a pick assembly as claimed in claim 1, the
method including: providing a first pick assembly comprising a
first holder body and a base body, attachable to a drive mechanism,
and a rotation member; in which the first holder body comprises a
first shaft and the base body comprises a base bore; the base bore,
the first shaft and the rotation member being cooperatively
configured such that the first shaft can be inserted within the
base bore, the rotation member being disposed between the first
shaft and the base bore, such that the first shaft will be capable
of rotation relative to the base bore when in use; removing the
rotation member and the first holder body; providing a second
holder body and an interference assembly comprising an interference
member; in which the second holder body comprises a head portion
and a second shaft depending from the head portion, the head
portion and a strike body being cooperatively configured such that
the strike body can be attached to the head portion, the strike
body comprising a super-hard strike tip; the second shaft and
interference assembly being cooperatively configured such that the
second shaft can be secured within the base bore, the interference
member disposed between the second shaft and the bore, frictional
interference between the second shaft, interference assembly and
base bore being sufficient to prevent rotation of the second shaft
within the base bore in use; the pick assembly comprising the base
body, the second holder body, the strike tip and the interference
member.
29. (canceled)
30. (canceled)
31. A method of using a processing assembly as claimed in claim 19,
the method including striking a work body by an end of the strike
body coterminous with the super-hard material and removing material
from the work body to provide a corresponding plurality of grooves,
each having a depth of at most 15 centimetres (cm).
32. (canceled)
33. A method as claimed in claim 20, in which the body to be
degraded comprises any of pavement, concrete or asphalt.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. national phase of International
Application No. PCT/EP2015/068333 filed on Aug. 10, 2015, and
published in English on Feb. 25, 2016 as International Publication
No. WO 2016/026725 A1, which application claims priority to United
Kingdom Patent Application No. 1414831.6 filed on Aug. 20, 2014,
the contents of all of which are incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] This disclosure relates generally to super-hard pick
assemblies, methods of providing them and for using them, and
processing assemblies comprising them; particularly but not
exclusively for pavement milling and texturing, or mining.
BACKGROUND OF THE INVENTION
[0003] U.S. Pat. No. 7,396,086 discloses a pick comprising a shank
attached to a base of a steel body, a cemented metal carbide core
press fit into the steel body opposite the shank, and a super-hard
impact tip bonded to a first end of the core opposite the shank. A
plurality of picks can be attached to a rotating drum connected to
the underside of a pavement recycling machine, which will bring the
picks into engagement with the pavement in use. A holder or block
is attached to the rotating drum, and the pick is inserted into the
holder. The holder or block may hold the pick at an angle offset
from the direction of rotation, such that the pick engages the
pavement at a preferential angle. Picks often rotate within their
holders or blocks upon impact with the pavement, which allows wear
to occur evenly around the pick, and the impact tip may be angled
to cause the pick to rotate within the bore of the holder. A
protective spring sleeve may be disposed around the shank both for
protection and to allow the high impact resistant pick to be press
fit into a holder while still allowing the pick to rotate. There is
a need for pick assemblies having extended working life,
particularly but not exclusively for fine milling (which may be
referred to as scarifying, grooving or roughening) pavement, such
as concrete pavement, and for efficient ways of providing them.
SUMMARY OF THE INVENTION
[0004] Viewed from a first aspect there is provided a pick assembly
comprising a holder body, a strike body, a base body attachable to
a drive mechanism, and an interference assembly comprising at least
one interference member; in which the holder body comprises a head
portion and a shaft depending from the head portion, the strike
body comprises a super-hard strike tip (i.e. a strike tip
comprising or consisting of super-hard material), the head portion
and the strike body are cooperatively configured such that the
strike body can be attached to the head portion, the strike tip
being exposed for striking a body to be degraded when in use (the
`body to be degraded` may be referred to as the `body to be
processed` or the `work body`), the base body comprises a base
bore; the base bore, shaft and interference assembly being
cooperatively configured such that the shaft can be secured within
the base bore, the interference member disposed between the shaft
and the bore, frictional interference between the shaft,
interference assembly and base bore being sufficient to prevent
rotation of the shaft within the base bore in use.
[0005] An advantage of this arrangement is that a pick assembly
with a holder body and strike body comprising a super-hard strike
tip can be non-rotationally attached to a base body that is
otherwise configured to rotationally hold a rotating strike body,
such as a strike body having a non-super-hard strike tip, for
example a carbide strike tip.
[0006] Various combinations and arrangements of pick tool
assemblies, processing assemblies (which may comprise degradation
assemblies) assemblies comprising them, methods for making them and
methods for using them are envisaged by this disclosure, of which
the following are non-limiting and non-exhaustive examples.
[0007] In some example arrangements, the combined radial margin of
interference between the shaft, the interference member and the
base bore may be at least 10, at least 20 or at least 30 microns;
and or at most 200 or at most 100 microns. In some examples, the
combined radial margin of interference between the shaft, the
interference member and the base bore may be 10 to 200 microns or
20 to 100 microns.
[0008] In some example arrangements, the interference member may
comprise a sleeve configured to be capable of accommodating and
clamping the shaft in a clamped condition, such that when the shaft
is in the clamped condition, the shaft and the sleeve can be
inserted into the base bore, the sleeve being disposed between the
shaft and the base bore. The diameter of the bore may be 10 to 200
microns, or 10 to 100 microns greater than the outermost diameter
of the sleeve.
[0009] In some example arrangements, the interference member may
comprise a sleeve or ring configured to be capable of accommodating
the shaft.
[0010] In various example arrangements, the shaft and base bore may
be spaced apart by the same distance all the way around the shaft,
or the distance by which the shaft and the base bore are spaced
apart may vary around the shaft. In some example arrangements, the
spacing between the side of the shaft and the inner side of the
base bore may be substantially the same all the way around the
shaft, with the interference member separating the shaft from the
bore by the substantially the same radial distance 360 degrees
around the shaft. In other examples, the spacing between the side
of the shaft and the inner side of the base bore may vary
substantially around the shaft, the interference member separating
the shaft from the bore by substantially different distances around
the shaft. In other words, the shaft and interference member may be
configured such that the shaft may be substantially coaxial or not
coaxial with the base bore, when assembled as for use (the
respective longitudinal axes being laterally displaced from each
other in the latter example arrangement).
[0011] In some example arrangements, the head portion may be
provided with a head bore, the bore and the strike body being
cooperatively configured such that the support body can be retained
within the head bore by frictional interference.
[0012] In some examples, the strike body may comprise a strike tip,
and the strike body and or the strike tip may comprise or consist
of grains of super-hard material such as synthetic or natural
diamond, a substantial number of which are directly inter-grown
(directly inter-bonded) with each other and comprise interstitial
regions between the diamond grains that include non-diamond
material such as cobalt, or at least some of the interstitial
regions may include voids devoid of solid state material. In some
example arrangements, the strike body may comprise a strike tip
comprising or consisting of polycrystalline diamond (PCD) material
or other super-hard material bonded to a cemented carbide
substrate. In some examples, the strike body may comprise or
consist of composite material comprising diamond and or cubic boron
nitride (cBN) grains dispersed within a matrix, which may comprise
or consist of cemented carbide material, alloy material,
super-alloy material (such as Ni-based super-alloy material),
ceramic material, cermet material, intermetallic phase material. In
some examples the strike body and or the strike tip may comprise or
consist of polycrystalline cBN (PCBN) material, and or silicon
carbide bonded diamond (SCD) composite material.
[0013] In some examples, the strike body may comprise a strike tip
joined to a support body. The strike tip may be joined to the
support body by means of a join layer comprising braze alloy
material, and the holder body may comprise a head bore for
accommodating and holding the strike body, configured such that
when the strike body is inserted into the head bore as for use, the
join layer is contained within the head bore.
[0014] In some example arrangements the shaft may be coaxial with
the support body and or the strike body when the strike body is
attached to the holder body as for use.
[0015] In some example arrangements, the base bore may comprise a
cylindrical inner surface and have a diameter of 18.00 to 21.00
millimetres (mm). In some example arrangements, at least a portion
of the shaft may be cylindrical in shape, and the diameter of the
portion of the shaft may be 16.00 to 19.00 millimetres (mm).
[0016] In some examples, the base bore may comprise a cylindrical
inner surface, at least an area of the side of the shaft may
comprise a cylindrical surface, and the interference member may
comprise a resilient sleeve configured to be capable of
accommodating the cylindrical area of the shaft and clamping it
with sufficient compressive force that the shaft will not rotate
relative to the sleeve in use. In some examples, the maximum
(radial) thickness of the sleeve or ring may be at least 1.20
millimetres (mm); and or at most 1.60, 1.45 or 1.35 millimetres
(mm). The mean thickness of the sleeve may be such as to allow it
function as a clip in relation to the shaft, by being capable of
expanding radially sufficiently to receive the shaft and to apply
compressive, clamping force onto the shaft to restrict, retard or
prevent its rotation within the sleeve.
[0017] In some example arrangements, the interference assembly or
member may comprise or consist of a resilient arm, ring or sleeve,
such as a spring clip or a leaf spring. In some example
arrangements, the interference member may be located between a
spring sleeve and the base bore when assembled as for use.
[0018] In some example arrangements, the interference member may
comprise or consist of elastomer material, such as synthetic or
natural rubber. In some examples the interference member may be in
the form of an O-ring. Example interference members (comprising
elastomer or other material) having various shapes in cross section
are envisaged, including circular, polygonal, square, rectangular
shaped cross sections. The interference member may be in the form
of a ring, sleeve or annular structure comprising or consisting of
elastomer material or other polymer material, which may be
configured for fitting around the shaft and contacting the base
bore when inserted into the base bore as in use. In some examples,
the ring may be generally square in cross section (the corners may
be rounded), such as of a kind that may be used in hydraulic or
pneumatic pistons, and which may be referred to as `quad-rings`.
The shape of an interference member in the general form of a ring
may affect its stiffness, and quad-rings may likely be stiffer than
O-rings, all else being equal.
[0019] In some example arrangements, the interference assembly may
comprise a laterally (or radially) extending portion that will be
located outside the base bore when assembled as for use, and which
may protect the base body in use.
[0020] In some example arrangements, the interference assembly may
be configured such that the shaft is spaced apart from the base
bore, solid material not being present to connect that portion and
the base bore. In other words, a substantially annular volume may
surround at least a portion of the shaft, the volume being empty of
solid material connecting the shaft and the base bore.
[0021] In some example arrangements, the interference assembly may
be configured such that a volume between the shaft and the base
bore contains material from a body being degraded by means of the
pick.
[0022] In various examples, the interference member may comprise or
consist of material that is sufficiently deformable or compliant
and sufficiently resilient that it can be forced into a volume
between the shaft and the base bore, and then resist rotation of
the shaft within the bore with sufficiently large force that the
shaft will not rotate in use. Example materials may include
elastomer and various polymer materials, and or relatively soft
alloys or metals such as copper or aluminum. In some example
arrangements, the interference member may comprise a relatively
hard and non-compliant material, the interference assembly being
configured such that it can be inserted between the shaft and the
base bore and substantially prevent the shaft from rotating in
use.
[0023] In some examples, the interference member may comprise
material, the coefficient of friction of which when in contact with
the base bore steel is greater than the coefficient of friction
between the material comprised in the shaft in contact with the
material comprised in the base bore.
[0024] In some example arrangements, the interference assembly may
comprise a plurality of interference members.
[0025] Viewed from a second aspect there is provided a processing
assembly comprising a plurality of disclosed pick assemblies, each
capable of being attached to a drive mechanism or carrier body.
Example processing assemblies may be suitable for processing
pavement in order to provide it with a substantially uniform
surface roughness and or to break up at least part of the pavement
(in other words, to degrade it). Example processing assemblies may
be suitable for use in mining or boring into the earth, such as for
breaking rock formations.
[0026] In some example arrangements, the base bodies may be
attached, such as welded, to a drum, which may be configured for
being attached to and driven to rotate by a drive vehicle.
[0027] In some example, the processing assembly may be suitable for
use in texturing (which may also be referred to as `scarifying` or
increasing the roughness of) structures such as pavement, and which
may comprise or consist of asphalt or concrete. The texturing may
involve breaking and removing material from a pavement to form a
plurality of grooves into it, corresponding to the respective pick
assemblies. After texturing, the grooves may exhibit a
substantially uniform roughness substantially, in which the mean
distance between the highest peak and lowest valley in each
sampling length may be at least about 3 or at least about 5
millimetres (mm); and or at most about 15 or at most about 10
millimetres (mm). The drive mechanism may comprise a drum, in which
a plurality of pick tools attached to the drum will be caused to
strike the pavement (or other body to be processed) as the drum is
driven by a vehicle to rotate (a pick assembly in the assembled
condition may be referred to as a pick tool).
[0028] Drums for pavement milling may be available in various
diameters and lengths, and may be capable of holding various
numbers of picks, depending on the drum dimensions and the nature
of the milling process to be carried out. For example, drums for
fine milling may have lengths of about 2.2 or 2 meters (m) and be
capable of holding about 748 or 672 pick tools, respectively. The
pick tool will likely be sufficiently small for use on drums
configured for achieving a relatively finely-structured texturing,
such drums potentially capable of at least 800 pick tools attached
to them.
[0029] In some example arrangements, a processing assembly may
comprise a drum capable of attachment to most about one pick tool
per 400 or per 100 square millimetres (mm.sup.2) over the surface
area of the drum the cylindrical side area). In other words, the
spacing between picks attached or attachable to the drum may be at
most about 20 or at most about 10 millimetres (mm). In some
examples, the drum may be capable of attachment to at least about
70 or at least about 90 pick tools per square metre (m.sup.2) of
the cylindrical side of the drum; in some example arrangements, the
drum may be capable of attachment to at most about 230, at most
about 160 or at most about 120 pick tools per square metre
(m.sup.2) of the cylindrical side of the drum. In some example
arrangements, the drum may be capable of attachment to 90 to 110
pick tools per square metre (m.sup.2) of the cylindrical side of
the drum. In various example arrangements, the drum may be
configured to be capable of attachment to a number of pick tools
per unit area (of the cylindrical side) such that the processing
apparatus is suitable for micro- or fine-milling of pavement.
[0030] In some example arrangements, the processing assembly may
comprise a plurality of pick assemblies attached to a drum suitable
for use cutting a plurality of substantially parallel grooves,
providing a surface roughness of up to 15 millimetres (mm) or up to
10 mm; and or at least 3 or at least 5 mm.
[0031] In some example arrangements, each of the shafts of all of
the pick assemblies may have the same diameter and the dimensions
of the respective interference members differ from each other to
account for differences in a base bore dimension.
[0032] In some example arrangements of processing assemblies, at
least some of the pick assemblies may be attached to the drive
mechanism such that when the strike body strikes a body to be
degraded with a force, the reaction force on the strike body will
result in the strike body experiencing an asymmetric torque about a
central cylindrical axis of the strike body. The frictional
interference force between the shaft, interference assembly and
base bore will be sufficient to defeat (in other words, to resist,
or be equal to or exceed) the torque and avoid rotation of the
strike body.
[0033] Viewed from a third aspect there is provided a method of
making a disclosed pick assembly, the method including providing a
first pick assembly comprising a first holder body and a base body,
attachable (and or attached) to a drive mechanism, and a rotation
member; in which the first holder body comprises a first shaft and
the base body comprises a base bore; the base bore, the first shaft
and the rotation member being cooperatively configured such that
the first shaft can be inserted within the base bore, the rotation
member being disposed between the first shaft and the base bore,
such that the first shaft will be capable of rotation relative to
the base bore when in use; the method including removing the
rotation member and the first holder body; providing a second
holder body and an interference assembly comprising an interference
member; in which the second holder body comprises a head portion
and a second shaft depending from the head portion, the head
portion and a strike body being cooperatively configured such that
the strike body can be attached to the head portion, the strike
body comprising a super-hard strike tip (which will be exposed when
the strike body is attached to the head portion as for use); the
shaft and interference assembly being cooperatively configured such
that the shaft can be secured within the base bore, the
interference member disposed between the shaft and the bore,
frictional interference between the shaft, interference assembly
and base bore being sufficient to prevent rotation of the shaft
within the base bore in use; the pick assembly comprising the base
body, the second holder body, the strike tip and the interference
member. The method may include assembling the pick assembly to
provide a pick tool.
[0034] In some examples, a strike body may be attached to the first
holder member, and the first strike body may be free of super-hard
material. For example the first strike body may comprise a first
strike tip comprising or consisting of cemented carbide material,
which may be coterminous with a strike surface that will engage a
body to be degraded when in use.
[0035] In some examples, the base body may be attached to a drive
mechanism, by welding for example.
[0036] Viewed from a fourth aspect there is provided a method of
using a disclosed processing assembly to degrade a body, such as to
texture the surface of the body, which may comprise or consist of
pavement.
[0037] The method including striking the body to be degraded by an
end of the strike body coterminous with the super-hard material and
removing material from the body to provide a corresponding
plurality of grooves, providing substantially uniform roughness of
at least about 3 or at least about 5 millimetres (mm); and or at
most about 15 or at most about 10 mm.
[0038] In some examples, the body to be degraded may comprise
pavement, and or may comprise asphalt or concrete.
BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Non-limiting example arrangements to illustrate the present
disclosure are described hereafter with reference to the
accompanying drawings, of which:
[0040] FIG. 1 shows a schematic, partly cut-away side view of an
example pick assembly attached to a drum (only a small part of
which is included in the illustration);
[0041] FIG. 2A shows a schematic side view of an example pick
assembly, partially cut-away to show a side view of the strike
body;
[0042] FIG. 2B shows a schematic side view of assembled components
of the example pick assembly, excluding the base body;
[0043] FIG. 2C shows a schematic side view of assembled components
of the example pick assembly excluding the base body, partially
cut-away to show part of a side view of the strike body; and
[0044] FIG. 2D shows a schematic cross section view of part of an
example base body for the example pick assembly of FIG. 2A;
[0045] FIG. 3 shows a schematic exploded side view of an example
holder body and an example strike body;
[0046] FIG. 4A shows a schematic side view of assembled components
of the example pick assembly excluding the base body, partially
cut-away to show a side view of the strike body;
[0047] FIG. 4B shows a schematic exploded side view of an example
holder body and an example strike body;
[0048] FIG. 5 shows a schematic perspective view of an example
interference assembly; and
[0049] FIG. 6 shows a schematic perspective view of an example
interference assembly attached to an example holder body.
DETAILED DESCRIPTION
[0050] With reference to FIG. 1, an example pick assembly may
comprise a holder body 10, a strike body 20, a base body 50 welded
to a drive mechanism 60, which may comprise a drum that can be
driven to rotate, and an interference member in the form of a
spring sleeve 30. The holder body 10 may comprise a head portion 12
and a cylindrical shaped shaft 14 depending from it, the shaft 14
and the spring sleeve 30 being cooperatively configured such that
both can be accommodated substantially non-rotatably within a base
bore 52 of the base body 50, having an inner diameter W0. The
strike body 20 may comprise a strike tip 22, comprising
polycrystalline diamond (PCD) material defining a rounded conical
end surface for engaging a body to be degraded, the strike tip 22
joined to a cemented carbide support body 24 attached to the head
portion 12 of the holder body 10.
[0051] With reference to FIG. 2A, FIG. 2B, FIG. 2D and FIG. 20, an
example pick assembly may comprise a steel holder body 10, a strike
body 20, a base body 50 attachable to a drive mechanism (not
shown), and an interference member in the form of a spring sleeve
30. The holder body 10 may comprise a head portion 12 and a
cylindrical shaped shaft 14 depending from it, the shaft 14 and the
spring sleeve 30 being cooperatively configured such that both can
be accommodated non-rotatably within a base bore 52 of the base
body 50, having an inner diameter W0. The strike body 20 may
comprise a strike tip 22, comprising a polycrystalline diamond
(PCD) structure joined to a cemented carbide substrate 24. The
outermost, exposed end of the strike tip 22 is defined by the PCD
material and an opposite end of the strike tip 22 is coterminous
with an end boundary of the substrate 25. In this example, the end
PCD surface has the shape of a blunted cone. The end boundary of
the substrate 25 is joined to an end of a generally cylindrical
cemented carbide support body 24 by a layer 23 consisting of braze
alloy material. In this example, the strike body 20 is fixed by
shrink fitting into a bore provided in a proximate end of the head
portion 12, coaxial with the shaft 14 depending from the opposite
end of the head portion 12. The bore in the head portion 12 (which
may be referred to as the `head bore`) is sufficiently large that
the layer 23 of braze material is contained within the head
bore.
[0052] A proximate end of the base bore 52 will have a bore mouth
54 for receiving the shaft 4 and the spring sleeve 30 (in
combination). In a particular example, the base bore diameter W0
may have a diameter about 50 microns larger than the outer diameter
W2 of spring sleeve (in other words, the interference margin may be
about 50 microns). In various examples, the overall margin of
frictional interference between the spring sleeve 30 (when clamping
the shaft 14 as for use) and the base bore 52 may be 10 to 100
microns, in order to prevent substantial rotation of the shaft 14
within the base bore 52 in use.
[0053] The proximate end of the base body may comprise or consist
of a generally annular surface area 56 surrounding the mouth 54 of
the base bore 52 and having an outer diameter W4. In various
examples, the surface area 56 may be substantially planar or
non-planar. In some examples, it may lie on a transverse plane
substantially perpendicular to the longitudinal axis of base body,
which will be coaxial with the inner surface of the base bore 52;
in other examples, at least a region of the surface area 56 may lie
at a non-zero angle to such a plane; for example, the surface area
56 may depend away from the mouth 54 at a non-zero angle to the
transverse plane. An annular washer 40 may be disposed between an
under-side of the head portion 12 and the surface area 56, which
extends radially in the example illustrated. The washer 40 may
consist of steel, have substantially the same outer diameter W4 as
the surface area 56 and thickness T1, which may be about 3 to 5
millimetres (mm). In a particular example, it may be about 4 mm. It
may function to provide a degree of wear protection for the surface
area 56.
[0054] In the particular example illustrated in FIG. 2A to FIG. 2D,
the shaft 14 may have a length L2 of about 39.5 mm, the head
portion may have a L1 of about 41.1 mm, the base bore 52 may have a
diameter W0 of 19.85 millimetres (mm) and the spring sleeve 30 may
have a generally annular wall thickness T of 1.30 millimetres (mm).
The spring sleeve wall thickness T may be sufficiently thin that it
will be sufficiently flexible to be capable of being radially
expanded to receive the shaft 14 and sufficiently resilient to hold
the shaft 14 by a radial frictional force in use. In general, the
thicker the annular wall of the spring sleeve 30, the more force
will likely be required to expand it to receive the shaft 14. The
flexibility and resilience of the spring sleeve 30 will likely be
affected by the mechanical properties of the material of which it
is formed, for example by the type of steel used. In some examples,
the inner diameter of the spring sleeve 30 may be at least
approximately 5 microns greater than the diameter W3 of the shaft
14. The largest diameter W3 of the cylindrical portion of the shaft
14 to be accommodated by the spring sleeve 30 is about 17.15
millimetres (mm). When the shaft 14 is accommodated by the spring
sleeve 30 as for use, the outer diameter W2 of the spring sleeve 30
will be the sum of the shaft diameter W3 and double the wall
thickness T of the spring sleeve 30. In this specific non-limiting
example, W2 will be 17.15 mm +2.times.1.30 mm=19.75 mm, which is
0.1 mm (100 microns) less than the inner diameter W0 of the base
bore 52. This example arrangement will thus provide a margin of
radial interference of about 100 microns (0.1 mm) between the shaft
14 and spring sleeve 30 on the on hand and the base bore 52 on the
other.
[0055] In other examples in which the inner diameter of the base
bore W0 may be about 19.85 millimetres (mm), the diameter of the
portion of the shaft 14 to be inserted into the spring sleeve may
be greater than 17.15 and the thickness T of the wall of the spring
sleeve may be less than 1.30 mm. Many arrangements are envisaged,
in which the diameter W0 base bore 52 may not have the value 19.85
mm (in some examples, the diameter W0 may be 18 to 22 mm), the
diameter W3 of the portion of the shaft 14 to be inserted into the
spring sleeve 30 may not have the value 17.15 and the thickness T
of the wall of the spring sleeve 30 may have the value in the range
of about 1.2 to about 1.6 mm, other than 1.30 mm. In such example
arrangements, the diameter W2 of the spring clip 30 when the shaft
14 has been inserted into it as for use may be 10 to 200 microns
less than the diameter W0 of the base bore 52. For example, the
inner diameter W0 of the base bore 52 may be 19.00 mm, the
thickness T of the wall of the spring sleeve 30 may be 1.20 mm, the
outer diameter W2 of the spring sleeve 30 when the shaft 14 is
inserted into it may be 18.75 mm and the diameter W3 of the shaft
14 may be 16.35 mm. In this example, the margin of frictional
interference between the spring sleeve 30 and the shaft 14 will be
25 microns.
[0056] In practice, dimensional tolerances of the diameters of
shafts and or the bore diameters may be 0.05 to 0.1, or up to about
0.20 millimetres (mm), which may need to be taken into account when
selecting or configuring interference members, and or in combining
particular holder bodies, interference members and base bodies.
[0057] In some examples, a plurality of holder bodies 10 may need
to be secured within a corresponding plurality of base bodies 50,
which may be secured by welding or other means to one or more drums
for road milling or mining, for example, and in which the base
bores 52 may have different diameters W0 from each other. One
example approach may be to provide the plurality of holder bodies
10 having substantially the same shaft diameters W3, and a
corresponding plurality of spring sleeves 30 having different wall
thicknesses T, each selected for a respective base body 50
according to its bore diameter W0 and the overall margin of
frictional interference required. In some circumstances, such an
approach may be relatively more efficient than using spring sleeves
having the same wall thicknesses T as each other and providing the
plurality of holder bodies 10 having different respective shaft
diameters W3. However, the latter approach or a combination of
approaches, in which the spring sleeve wall thicknesses T and the
shaft diameters W3 are different from each other within the
respective pluralities, are also envisaged within the scope of this
disclosure.
[0058] About 35 example pick tools as described with reference to
FIG. 2A to FIG. 2D were tested by using them to form chambers on a
concrete road pavement. The base holder and drum were commercially
available products. For comparison, commercially available pick
assemblies configured to allow the holder body to rotate within the
base bore and in which the strike bodies comprised cemented carbide
tips were also used. The example pick assembly appeared to be
effective in substantially preventing the holder bodies from
rotating in use and in penetrating the concrete to a depth of up to
10 mm, under relatively high stress owing to the fact that they
were relatively widely spaced apart from each other on the milling
drum (the spacing between the example pick assemblies was
substantially greater that they would be on a drum to be used for
`fine` milling operations in practice). In this trial, the example
pick tools exhibited at least about 6 to 10 times longer working
life than comparison pick assemblies, the tips formed by the
super-hard material substantially maintaining their shapes over the
extended working life.
[0059] In various kinds of applications such as pavement grooving,
the aspect of super-hard tips maintaining their desired shape for
an extended period will likely result in the shapes and sizes of
the grooves to remain substantially constant throughout the
operation, with fewer changes of picks.
[0060] With reference to FIG. 3 an example pick assembly may
comprise a holder body 10 and strike body 20. The holder body 10
comprises head portion 12 provided with a head bore 16 at a
proximate end for accommodating the strike body 20, and a shaft 14
extending from a distal end of the head portion 12. The strike body
20 may comprise polycrystalline diamond (POD) material 22 defining
a dome-shaped end surface for striking a body to be degraded. The
lengths L1, L2 of the head portion 12 and shaft 14, respectively,
may be 39 mm and 38 mm, and the largest diameter W0 of the shaft
may be 17.35 mm.
[0061] With reference to FIG. 4A and FIG. 4B, an example pick
assembly may comprise a holder body 10 having a head portion 12 and
a shaft 14 extending from a base of the head portion 12, as well as
a spring sleeve 30 and wear protection ring 40, in which the
thickness T1 of and outer diameter W2 of the wear protection ring
40, and the lengths L1, L2, L3 of the head portion 12, shaft 14 and
spring sleeve 30, respectively, had the same values as in the pick
assembly described with reference to FIG. 2A to FIG. 2D. The head
bore 16 for accommodating the strike body 20 had a depth of 2.9 mm.
The strike body 20 may comprise polycrystalline diamond (PCD)
material 22 defining a blunted cone end surface and bonded to a
cemented carbide substrate 25, which is joined by a layer 23 of
braze material to the support body 24. In this example, proximate
end of the support body 24 adjacent the braze layer 23 is
substantially the same as the diameter of the substrate 25, which
may be about 12 mm, and the distal end to be joined to the head
bore 16 of the holder body 10 may have a substantially greater
diameter of 21.8 mm, the side of the support body 24 connecting the
opposite end curving divergently outward (transversely, or
radially). In this example, the distal end of the support body 24
may be joined to a bottom surface within the head bore 16 by braze
material or adhesive, for example.
[0062] With reference to FIG. 5, the interference assembly 30 may
comprise a spring sleeve 32 and an interference member 34 that will
be located between the spring sleeve 30 and the base bore (not
shown) when assembled as for use. The interference assembly 30 may
comprise a laterally extending portion 40 at a proximate end, which
may abut or be spaced apart from the surface area of the base body
surrounding the base bore when assembled as for use, potentially
providing a degree of protection for the base body against wear in
use. The spring sleeve 32 will clamp around a shaft of a holder
body (not shown in FIG. 5) inserted into it, such that the shaft
will be unable to rotate substantially relative to the spring
sleeve 32 in use. The interference member 34 may comprise or
consist of material having a relatively high coefficient of
friction when in contact with steel and may be ring (for example,
an `O-ring`) or cylindrically shaped, and may be referred to as an
`interference ring` 34. For example, the interference ring 34 may
comprise or consist of elastomeric material such as rubber (for
example, natural rubber). The interference ring 34 will be
configured such that the area of contact between the spring sleeve
32 on the one side and the base bore on the opposite side is
sufficiently great that the spring sleeve 32 containing the shaft
of a holder body will not substantially rotate within the base bore
in use. The configuration of the interference ring 34 to achieve
this effect will likely depend on the material comprised in it, and
more particularly, the friction properties of the material. In the
example arrangement illustrated in FIG. 5, a major side area of the
spring sleeve will be spaced apart from the inner surface of the
base bore, since the interference member 34 contacts only a minor
side area of the spring sleeve 32. In use, a gap between the side
of the spring sleeve 32 and the inner base bore surface may become
filled with material removed from a body, which may increase the
frictional forces between the spring sleeve 32 and the base bore
and contribute to the effect of preventing the spring sleeve 32
from rotating within the base bore. In some examples, more than one
interference member 34 may be present.
[0063] With reference to FIG. 6, an example interference assembly
may comprise one or more interference rings 30A, 30B in contact
with the shaft 14 extending from a head portion 12 of a holder
body. In such examples, a spring sleeve may not be required and the
interference rings 30A, 30B will function substantially as
described above with reference to FIG. 5.
[0064] In examples such as described with reference to FIG. 5 and
FIG. 6, there may be a risk of the interference member 34, 30A, 30B
becoming less effective during use, by being compressed or
deformed. However, the potential accumulation of debris in the gap
or gaps between the base bore and the spring sleeve or the shaft,
as the case may be, may have a significant effect in some examples
in reducing or preventing the holder body rotating relative to the
base body. In such examples, the interference member 34, 30A, 308
may not need to function optimally throughout the entire working
life of the pick assembly, but potentially only for a sufficiently
long period for a sufficient amount of debris to accumulate in the
gap between the spring sleeve 32 or shaft 14 and the base bore.
[0065] In certain example applications, such as fine milling of
pavement (in which the pick tools are relatively closely spaced
apart), pick assemblies attached to drive mechanisms such as drums
may be used to cut series of substantially parallel and relatively
shallow grooves into a body. For example, pick assemblies attached
to drums may be used to cut a plurality of substantially parallel
grooves having a depth of up to 15 or up to 10 mm into concrete
pavement. It may be desired for the grooves to have substantially
the same cross sectional profile and depth as each other, and for
these features to remain substantially unchanged throughout the
operation, with as few replacements of pick tools as possible.
However, the shapes of the pick tips that engage and degrade the
body will tend to change with use, as they are abrasively worn by
the material comprised in the body being processed. It may be
desired that the pick tips wear slowly, at substantially the same
rate and in substantially the same way as each other, so that
changes in the shapes and sizes of the grooves that may occur over
time will be as consistent as possible. If a pick breaks, for
example by fracturing on striking a relatively harder object within
the pavement, or due to imperfections in the material comprised in
the pick tip, then all the pick tools on a drum may need to be
replaced. If only the fractured pick tool is replaced, its shape
profile will likely differ from that of the other picks because it
will not have undergone abrasive wear; consequently, the groove
that it will produce may have different characteristics from the
other grooves. Replacement of all pick tools may be time consuming
and costly because in some applications, each drum may hold several
hundred pick tools (for example, in excess of 700 pick tools). In
order for cemented carbide tips to wear evenly and at similar
rates, pick assemblies for various applications may be configured
such that the holder body will be capable of rotating about its
longitudinal axis within the base bore in use. Promoting rotation
of carbide pick tips when they engage the body may result in more
even wear around the axis of rotation and extend the working life
of the carbide-tipped pick. In general, this may be promoted by
mounting the base bodies onto a drum at a slight angle (for
example, about 5 degrees) to the direction of travel of the pick
tip in use, and a spring sleeve between the shaft of the holder
body and the base bore may have the effect of permitting rotation
of the holder body in use. Promotion of rotation of super-hard
tipped picks may not be as effective as for carbide tips, and may
not be necessary.
[0066] Since super-hard material such as polycrystalline diamond
(PCD) material is substantially more resistant to abrasive wear
then cemented carbide material, pick tools comprising super-hard
tips will likely have the aspect of substantially extended working
life, during which their initial shapes will be preserved for
substantially longer periods of time. Unfortunately, super-hard
material is generally substantially more brittle than cemented
carbide and the risk of fracture when used in impact applications
such as pavement milling may generally be very substantially higher
than that for cemented carbide material. In addition, super-hard
tips for picks will likely be substantially more costly to provide
than cemented carbide tips. In order for super-hard tipped pick
tools to be viable in certain example applications, the risk of
fracture and or of differential wear will likely need to be reduced
as much as possible.
[0067] Example disclosed pick assemblies have the aspect of
extended working life and retention of their shape in certain
example applications. While wishing not to be bound by a particular
theory, this may arise from achieving substantially reduced risk of
fracture and differential wear of the super-hard tips; which may
arise from reduced scope for movement of the shaft within the base
bore. Configuration of the shaft, interference member and base bore
such that the holder body is prevented from substantial rotation in
use appears to reduce the potential amount of transverse or radial
movement that the holder body can experience in use. In other
words, if these dimensions permit rotation of the holder body about
its longitudinal axis, other movements within the base bore will
likely be permitted to some extent; for example.sub.; a kind of
`rattle fit` or `chatter` of the holder body may be permitted. This
may permit sufficient lateral movement for the super-hard tip to
engage the body being degraded at slightly varying contact angles,
which may increase the risk of fracture and or uneven wear of the
super-hard material.
[0068] Consequently, the mean working life of the picks may be
reduced and or the statistical distribution of their working lives
may widen, making their performance relatively less predictable. In
addition, the risk of the shaft wearing as a result of rotation
against the wall of the base bore and or a spring sleeve will be
negligible if the shaft is substantially prevented from rotating.
This risk would likely be higher for super-hard tipped picks since
the tips will tend to wear much more slowly and the potential
working life of the pick tool will be correspondingly higher.
[0069] An aspect of an example method of making an example pick
assembly may be that a processing assembly comprising a plurality
of cemented carbide-tipped pick tools, in which the pick tips are
urged to rotate about their own longitudinal axes in use, can be
adapted relatively efficiently and quickly to comprise a plurality
of super-hard tipped pick tools, in which the pick tips do not
rotate relative to the base body in use.
[0070] When picks comprising super-hard tips are used in at least
some applications, the aspect of reducing or eliminating movement
of the holder body relative to the base body appears to exceed
potential benefits of allowing the picks to rotate in use.
Disclosed example pick assemblies may have the aspect of extended
working life and or improved quality and consistency of the surface
finish of the processed body.
[0071] Certain terms and concepts as used herein are briefly
explained below.
[0072] In general, as used herein, `super-hard material` has a
Vickers hardness (HV) of at least about 28 gigapascals (GPa).
Synthetic and natural diamond, polycrystalline diamond (PCD), cubic
boron nitride (cBN) and polycrystalline cBN (PCBN) material are
examples of super-hard materials. As used herein, synthetic
diamond, which is also called man-made diamond, is diamond material
that has been manufactured. As used herein, polycrystalline diamond
(PCD) material comprises an aggregation of a plurality of diamond
grains, a substantial portion of which are directly inter-bonded
with each other and in which the content of diamond is at least
about 80 volume per cent of the PCD material. Interstices between
the diamond grains may be at least partly filled with a filler
material that may comprise catalyst material for synthetic diamond,
or they may be substantially empty. As used herein, a catalyst
material (which may also be referred to a solvent/catalyst
material) for synthetic diamond is capable of promoting the growth
of synthetic diamond grains and or the direct inter-growth of
synthetic or natural diamond grains at a temperature and pressure
at which synthetic or natural diamond is thermodynamically stable.
Examples of catalyst materials for diamond are Fe, Ni, Co and Mn,
and certain alloys including these. Bodies comprising PCD material
may comprise at least a region from which catalyst material has
been removed from the interstices, leaving interstitial voids
between the diamond grains. As used herein, PCBN material comprises
grains of cubic boron nitride (cBN) dispersed within a matrix,
which may comprise metal, alloys, intermetallic materials, Ni-based
super-alloy material or ceramic material, for example.
[0073] Other examples of super-hard materials include certain
composite materials comprising diamond or cBN grains held together
by a matrix comprising ceramic material, such as silicon carbide
(SiC), or cemented carbide material, such as Co-bonded WC material
(for example, as described in U.S. Pat. Nos. 5,453,105 or
6,919,040). For example, certain SiC-bonded diamond materials may
comprise at least about 30 volume per cent diamond grains dispersed
in a SiC matrix (which may contain a minor amount of Si in a form
other than SiC). Examples of SiC-bonded diamond materials are
described in U.S. Pat. Nos. 7,008,672; 6,709,747; 6,179,886;
6,447,852; and International Application publication number
WO20091013713).
[0074] As used herein, a shrink fit is a kind of interference fit
between components achieved by a relative size change in at least
one of the components (the shape may also change somewhat). This is
usually achieved by heating or cooling one component before
assembly and allowing it to return to the ambient temperature after
assembly. Shrink-fitting is understood to be contrasted with
press-fitting, in which a component is forced into a head bore or
recess within another component, which may involve generating
substantial frictional stress between the components and
potentially some surface deformation.
[0075] As used herein, the phrase `radial margin of interference`
is the difference in a radial dimension between a bore and a body
accommodated by the bore, the bore dimension being greater than the
corresponding dimension of the body. For example, if the respective
lateral (radial) cross sections of the bore and of the part of the
body inserted into the bore are circular, the radial margin of
interference will be the difference in diameter between the
circular cross sections, provided that the diameter of the bore
will be greater than that of the body and that the diameters are
sufficiently similar for a degree of frictional interference to be
evident between the bore and the body. In various other examples,
the transverse or radial cross section may be non-circular, such as
polygonal or elliptical, or different regions of the cross section
shape may be different shapes. In such examples, the radial margin
of interference will refer to the corresponding dimensions of the
bore and body for which the difference between them is
smallest.
[0076] In example arrangements in which an assembly, body or part
or a body has a generally cylindrical shape (a degree of
cylindrical symmetry), the use of terminology associated with a
cylindrical coordinate system may be helpful for describing the
spatial relationship between features. In particular, a
`cylindrical` or `longitudinal` axis may be said to pass through
the centres of each of a pair of opposite ends and the body or a
part of it may have a degree of rotational symmetry about this
axis. Planes perpendicular to the longitudinal axis may be referred
to as `lateral` or `radial` planes and the distances of points on
the lateral plane from the longitudinal axis may be referred to as
`radial distances`, `radial positions` or the like. Directions
towards or away from the longitudinal axis on a lateral plane may
be referred to as `radial directions`. The term `azimuthal` will
refer to directions or positions on a lateral plane,
circumferentially about the longitudinal axis.
[0077] As used herein, the term `surface texture` (which may be
referred to simply as `texture`) includes surface roughness, which
is quantified by the vertical deviations of a real surface from a
substantially planar ideal form. Pavement may be mechanically
treated to provide it with texture and exhibit a degree of
roughness. As used herein, roughness will mean the average distance
between the highest peak and lowest valley in each sampling
length.
* * * * *