U.S. patent application number 10/120083 was filed with the patent office on 2003-01-23 for bit holders and bit blocks for road milling, mining and trenching equipment.
Invention is credited to Sollami, Phillip A..
Application Number | 20030015907 10/120083 |
Document ID | / |
Family ID | 26956363 |
Filed Date | 2003-01-23 |
United States Patent
Application |
20030015907 |
Kind Code |
A1 |
Sollami, Phillip A. |
January 23, 2003 |
Bit holders and bit blocks for road milling, mining and trenching
equipment
Abstract
An improved bit holder with its mating bit block is disclosed
utilizing a slight taper in the bit block bore, and a tapered shank
on the bit holder that includes a second larger diameter tapered
distal segment that combines with an axially oriented slot through
the side wall of the bit holder shank to allow a substantially
larger interference fit between the distal tapered shank segment
and the bit block bore than previously known. When inserting the
bit holder in the bit block bore, the distal first tapered segment
resiliently collapses to allow insertion of that segment into the
bit block bore. A second shank tapered portion axially inwardly of
the first distal tapered portion, and separated therefrom by a
shoulder provides a space between the bit block bore and the second
tapered shank portion until the upper 1/8 to 1/2 inch of the second
tapered shank portion meets and again forms an interference fit
with the bit block bore at a portion of the shank above a
termination of the slot therethrough. The dual tapered shank allows
the insertion of the bit holder in the bit block with an
interference fit that provides a secure mounting of the bit holder
in the bit block. Since there is no fastener to maintain the bit
holder in the bit block, it may be removed from the bit block by
driving the base of the bit holder out of the bit block.
Inventors: |
Sollami, Phillip A.;
(Herrin, IL) |
Correspondence
Address: |
JAMES N VIDEBECK
1 S 376 SUMMIT AVE
COURT C
OAKBROOK TERRACE
IL
60181
US
|
Family ID: |
26956363 |
Appl. No.: |
10/120083 |
Filed: |
April 9, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10120083 |
Apr 9, 2002 |
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09500983 |
Feb 15, 2000 |
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6371567 |
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09500983 |
Feb 15, 2000 |
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09273690 |
Mar 22, 1999 |
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6364420 |
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Current U.S.
Class: |
299/104 ;
299/106 |
Current CPC
Class: |
B28D 1/188 20130101;
E21C 35/191 20200501; E21C 35/197 20130101; E21C 35/188
20200501 |
Class at
Publication: |
299/104 ;
299/106 |
International
Class: |
E21C 025/10 |
Claims
What is claimed:
1. A bit holder for use in road milling, trenching and mining
equipment as part of an assembly including a bit, bit holder and
bit block, said bit being mountable in a first bore through said
bit holder and said bit holder being mountable in a second bore
through said bit block, said bit holder comprising: a bit receiving
front portion terminating at an annular flange for engaging a face
of said bit block, a shank portion extending axially rearwardly
from said annular flange, said shank portion including a declining
taper from adjacent said annular flange to adjacent a distal end
thereof, said declining taper providing an interference fit between
said bit holder and said bit block.
2. The bit holder as defined in claim 1 wherein said shank portion
includes an axial bore centrally therethrough, and means on said
shank portion for providing increased resilience for an outer
surface of said declining taper to increase the usable interference
fit between said declining taper and said second bore on said bit
block by an least about four times a standard interference fit
therebetween.
3. The bit holder as defined in claim 2 wherein said means for
providing increased resilience for an outer surface of said
declining taper includes a radial slot through one half of said
shank portion from said outer surface of said declining taper to
said axial bore centrally therethrough, said slot extending axially
from said distal end of said shank to a slot terminating a
predetermined axial distance from said annular flange.
4. The bit holder as defined in claim 1 wherein said declining
taper includes a first taper portion extending on said shank from
adjacent said annular flange to a predetermined position between
said annular flange and said distal end thereof, a shoulder having
a radially extending component thereof positioned at said
predetermined position and a second taper portion extending from
said shoulder to a position adjacent said distal end of said
shank.
5. The bit holder as defined in claim 4 wherein said first and
second taper portions have identical tapers.
6. The bit holder as defined in claim 4 wherein, the insertion of
said second taper portion of said shank in said bit block bore
lessens an outer diameter of said first taper portion of said shank
to an extent that an actual interference fit between said first
taper portion and said bit block bore is achieved only at about the
last 1/4 to 5/8 inch of insertion of said shank in said bit block
bore.
7. The bit holder as defined in claim 4 wherein each of said first
taper portion, shoulder and second taper portion of said shank is
sized to be an interference fit with said bit block bore prior to
inserting said shank in said bit block bore.
8. A bit block including a bore therethrough for insertion of a bit
holder therein, an improvement comprising, detent means extending
radially inwardly from a surface of rotational movement of any
slotted bit holder inserted in said bore.
11. A bit holder and bit block in combination, comprising: a bit
block including a body having means thereon for mounting said body
to an external member, and a bore for receiving a bit holder
positioned through said body extending from a substantially flat
front face to a rear portion thereof, said bore being tapered from
about 1 degree per side to about 4 degrees per side from said front
face to said rear portion, a bit holder including a front portion,
a shank portion thereadjacent, a radial flange at the rear of said
front portion and a bit retaining bore axially therethrough, said
shank portion being tapered for an interference fit with said bore
through said bit block, and including a radial slot through one
half of said shank portion from an outer surface of said taper to
said bit retaining bore along a substantial length of said shank
portion, locating detent means on one of said bit block and bit
holder for positioning-said holder in predetermined rotational
orientation with the other, and complementary recess means on the
other of said bit holder and bit block for receiving said locating
detent means.
12. The combination as defined in claim 11 wherein, said detent
means includes a locator pin extending into said bore on said bit
block, and said recess means includes a slot through said shank
from said bit retaining bore to an outer surface thereof, and
extending from a distal end of said shank to a predetermined
position thereon adjacent said radial flange.
13. The combination as defined in claim 11 wherein, said detent
means includes a locating pin on one of said front face of said bit
block and said radial flange of said front portion of said bit
holder, and said recess means includes a slot on the other of said
front face and said radial flange, said recess means being larger
than said detent means in an arcuate direction to provide a
predetermined amount of adjustability of rotational orientation
between said bit block and said bit holder.
14. The combination as defined in claim 11 wherein said bit holder
shank portion includes a first taper segment extending on said
shank from adjacent said annular flange to a predetermined position
between said radial flange and said distal end thereof, a shoulder
having a radially extending component thereof positioned at said
predetermined position and a second taper segment extending from
said shoulder to a position adjacent said distal end of said
shank.
15. The combination as defined in claim 14 wherein said first and
second taper segments have identical tapers.
16. The combination as defined in claim 14 wherein said first and
second taper segments have differing tapers.
17. The combination as defined in claim 14 wherein, the insertion
of said second taper segment of said shank in said bit block bore
lessens an outer diameter of said first taper segment of said shank
to an extent that an actual interference fit between said first
taper segment and said bit block bore is achieved only at about the
last 1/4 to 5/8 inch of insertion of said shank in said bit block
bore.
18. The combination as defined in claim 14 wherein each of said
first taper segment shoulder and second taper segment of said shank
is sized to be an interference fit with said bit block bore prior
to inserting said shank in said bit block bore.
Description
[0001] This invention relates generally to road surface removal or
reclaimer-stabilizer equipment and mining equipment, and more
particularly, to cutter bit holders and bit blocks used in such
road milling, mining, and trenching equipment. This is a
continuation-in-part of Ser. No. 273,690 filed Mar. 22, 1999.
BACKGROUND OF THE INVENTION
[0002] Cutter bits are utilized in road, off-road and mining
machinery on the perimeter and across the width of a rotary drum or
on the outside of a continuous chain or the like where the bits are
moved through an orbit which is intercepted by the face of the
material being removed or recycled. Road milling equipment removes
the defective surface of a road and smooths the top of all or
selected portions of the road surface. The bits include a tip and a
shank. The shank is received and may axially rotate in a bit holder
which is secured onto a bit block that, in turn, is mounted on the
drum. Each of the bits has a hardened tip, preferably made of
tungsten carbide or such other hardened material that acts to
remove a portion of the surface it contacts. By using a sufficient
number of these bits around the outer surface of a rotating drum, a
large amount of surface may be worked. Any surface being worked
generally has a hardness which can be measured or anticipated prior
to the removal operation. However, such road surfaces, or surfaces
being removed have hardened irregularities running therethrough.
The toughness or hardness of the irregularities may result in the
breakage of the bits and holders as they are being run over such
irregularities.
[0003] Additionally, a need has developed for providing ease of
removability of bits in their bit holders, especially when the bit
becomes worn and in need of replacement. U.S. Pat. No. 5,374,111
discloses an undercut flange at the bottom of a base of a bit that
allows a pry bar to be wedged between that flange and the top of
the bit block (no bit holder in this patent) to help remove a bit
from a bit block. It would be desirable to provide a more efficient
means for allowing the removal of a bit from a bit holder or a bit
block.
[0004] Additionally, tightening a small fastener on the bottom of a
bit holder to hold it in the bit block concentrates friction forces
on a small area of the nut top face and the bottom of the bit
block. It would be desirable to spread those friction forces over a
larger area and avoid the use of a nut to retain the bit holder on
the bit block.
[0005] Further, a need has developed for a truly quick-change type
of bit holder that may easily and quickly be both inserted in the
bit block and removed therefrom.
[0006] It is, therefore, an object of the present invention,
generally stated, to provide an improved means for quickly mounting
and/or removing a bit holder from its associated bit block.
[0007] Another object of the present invention is the provision of
an improved means for mounting a bit holder in a bit block without
the use of retaining nuts, clips or the like.
[0008] A further object of the invention is the provision of
retaining a bit holder in a bit block by means of a resilient
interference fit between the holder and the block.
[0009] Another object of the invention is the provision of an
improved means for providing for breakage of inexpensive
replaceable parts when road resurfacing equipment and mining
equipment bits encounter very hard irregularities in the surface
being milled or mined.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The features of the present invention which are believed to
be novel are set forth with particularity in the attached claims.
The invention may best be understood by reference to the following
description taken in conjunction with the accompanying drawings in
which like numerals refer to like parts, and in which:
[0011] FIG. 1 is a side elevational view of a bit block, bit holder
and bit assembly constructed in accordance with the present
invention;
[0012] FIG. 2 is an exploded side elevational view of the assembly
shown in FIG. 1;
[0013] FIG. 3 is a side elevational view of a second embodiment of
a bit holder constructed in accordance with the present
invention;
[0014] FIG. 4 is a top plan view of the bit holder shown in FIG.
3;
[0015] FIG. 5 is a side elevational view of a second embodiment of
a bit block for retaining the bit holder shown in FIGS. 3 and
4;
[0016] FIG. 6 is a top plan view of the bit holder shown in FIG.
5;
[0017] FIG. 7 is a side elevational view of the second embodiment
including a bit, bit holder and bit block assembly;
[0018] FIG. 8 is a bottom plan view of the second embodiment shown
in FIG. 7;
[0019] FIG. 9 is a side elevational view of a third embodiment of a
bit holder constructed in accordance with the present
invention.
[0020] FIG. 10 is a top plan view of the bit holder shown in FIG.
9;
[0021] FIG. 11 is a side elevational view of the third embodiment
bit holder being manually hammered into its bit block;
[0022] FIG. 11a is a side elevational view of the third embodiment
bit holder being manually hammered out of its bit block;
[0023] FIG. 12 is a side elevational view of a fourth embodiment
combination bit block/bit holder utilizing a long bolt and bottom
nut to press fit the bit holder onto the bit block.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Referring to FIGS. 1-2, a bit mounting assembly, generally
indicated at 20, constructed in accordance with the present
invention, includes a bit, generally indicated at 21, which is
mounted on a bit holder, generally indicated at 22, which, in turn,
is secured on a bit block, generally indicated at 23. The bit block
23 is one of a plurality of such blocks mounted around the outside
of the generally circular drum (not shown) or on a movable chain or
track (not shown).
[0025] Referring to FIG. 2, the bit, generally indicated at 21,
includes a forward end 24, and a shank 25 or rear end thereof. The
forward end 24 includes a hardened nose 26, preferably made of
tungsten carbide or a like material, a middle tapered portion 27
including a reduced diameter area 27a and a bottom flange portion
28 which is made so as to rest on the bit holder, generally
indicated at 22. A spring steel retaining clip 30 is positioned
over the shank 25 of bit 21 and is shaped so that when the bit 21
is inserted in the bit holder 22, the retaining clip 30 will secure
the bit therein while allowing it to rotate from external
forces.
[0026] The bit holder 22, constructed in accordance with the
present invention, includes a generally flat annular leading
surface 31 on which the rear side of the bit flange 28 rests when
inserted therein. Adjacent the annular leading surface 31 is a
middle or tapered portion 32 that ends in an enlarged flange
portion 33. In the preferred embodiment of the invention, a
plurality of notches, flats or indents 32a-d extend radially
inwardly of the middle tapered portion from top surface 31 toward
the flange 33. The back side 34 of flange 33 is an annular flat
surface which rests on the bit block 23 when mounted thereon, and
includes one aspect of the present invention to be discussed below.
Rearwardly adjacent the flange portion 33 is a reduced diameter
cylindrical shank portion 35 and a shoulder portion 36 which may
vary in length depending on its function, an undercut portion 37 is
next to the shoulder portion 36, and the bit holder terminates in a
threaded portion 38 adjacent the distal end 44 thereof. If the nose
26 of bit 21 hits a hard discontinuity, bit 21 will fail first, the
bit holder in this embodiment may be engineered to fail next across
reduced diameter section 37. The configuration allows the bit
holder to tumble out of bit block bore 49 after failure.
[0027] Also shown in FIG. 2 is a bore 40 that extends axially
through bit holder 22 from a countersink 41 in communication with
the front face 31, through the tapered portion 32, the flange
portion 33 and a substantial portion of the shank 35, 36 where it
narrows at chamfer 42 to a smaller diameter bore 43. Bore 43
extends the remainder of the bit holder to its distal end 44, or it
may be increased in diameter partly along its length to decrease
the cross sectional reduced diameter section 37, if desired. The
length of the bore 40 is determined partly by the length of the
shank 25 on bit 21. The shank 25 fits within bore 40, and is
retained therein by the spring steel retainer 30. If the bit 21
should break at reduced diameter portion 29 adjacent the bottom
flanged portion 28, a rod, punch, etc. (not shown) may be inserted
into the bottom of the bore to push the shank out of the
holder.
[0028] The bit block 23 consists of a base portion 45 that mounts
to a drum, chain, or track (not shown) and an angled bit holder
mounting portion 46 extending from the base 45 that includes a top
face 47, and a bottom recessed slot 48 which provides the opposing
ends for a bore 49, which may be tapered, and a reduced bridging
portion 51 extending from a bottom of bore 49 to the recessed slot
48. Bore 49 is sized to receive the cylindrical shank 35 of the bit
holder 22 with the annular flat surface 34 on the bottom of the
flange portion 33 resting on the top surface 47 of the bit block
mounting portion 46. In one important aspect of the present
invention, the surface area of contact between flange bottom 34 and
bit block top 47 is much greater than the surface area of contact
between the top 52a of nut 52 and nut contacting surface on slot 48
and will be discussed in greater detail below. The threaded portion
38 adjacent the distal end 44 of bit holder 22 extends through the
reduced passageway 51 where a nut 52 may be threaded thereon by
rotating the bit holder until its top surface 52a engages the
surface of the recessed slot 48 to retain the bit holder 22 on the
bit block 23.
[0029] Referring to FIG. 1, the distal end of a pneumatically
operated chisel is shown in dotted line at 55, inserted in one of
the notches 32C as more fully shown in FIGS. 3 and 4. The notches
32a-32d, constructed in accordance with the present Ad invention,
allow for the quick removal of the bit 21 from the bit holder 22 by
applying a force having a substantial axial component thereto to
the bottom side of the bit flange 28. In the preferred embodiments
there may be two, three or four notches or indents 32a-d (FIG. 2,
32-d not shown) on the bit holder 22 positioned at 120 degree or 90
degree intervals, respectively, around the circumference thereof.
Each notch may be straight vertically or slightly wider at surface
31 and narrows as the notch descends toward flange 33. While the
use of the punch 55 on one notch is usually sufficient to remove
the bit, the punch may be utilized sequentially in differing
notches to balance the axial force, if necessary, to move the bit
21 out of the bit holder 22.
[0030] Referring to FIGS. 3-8, a second embodiment of the bit
holder and bit block constructed in accordance with the present
invention is shown and described. Beginning at FIG. 3, a second
embodiment of the bit holder, generally indicated at 60, is
constructed to be a press fit into the bit block, generally
indicated at 61, shown in FIG. 5. The mounting of the bit holder 60
on the bit block 61 is accomplished without the aid of a retaining
nut, such as shown at 52 in the first embodiment, a spring
retaining clip or other fastening device utilized on the bottom of
the bit block 61.
[0031] Referring to FIGS. 3 and 4, similarly to bit holder 22, the
bit holder 60 has a flat annular leading surface 62, a middle
tapered portion 63 behind the flat annular leading surface 62 that
also includes a pair of notches 64-65, 120 degrees apart and having
the same function as the notches 32a-d in the first embodiment and
an annular groove 63a whose depth is calculated to insure that, in
case of the bit hitting a hard discontinuity, the bit holder will
break at groove 63a rather than the bit block 61 separating at its
weldment to the drum or chain. Additionally, the rear of the middle
tapered portion 63 is an enlarged flange portion 66 including an
annular flange backside 67 similar to that shown in the first
embodiment 22. A locator pin 69 extending from the flange back side
67 fits loosely into a clearance hole 69a on bit block top surface
85 (FIG. 5) for limiting the rotation of holder 60 when mounted on
the bit block 61. If the bit holder breaks, the pin 69 falls out of
hole 69a and does not damage the bit block 61. To the rear of the
annular flange backside is the shank portion of the bit holder,
generally indicated at 68. An undercut 70 between the annular
flange backside 67 and the shank portion 68 assures lob that stress
points are avoided between the shank and the enlarged flange
portion when the bit holder 60 is mounted in the bit block 61. This
undercut 70 also provides a breaking point if undercut 63a is not
used.
[0032] Flange 66 is annular in that a bore 71 runs axially through
the bit holder in a more straight forward hollow cylindrical manner
than the bore 40 which extends through the bit holder 22 of the
first embodiment. The leading edge of bore 71 includes a
countersink 72 adjacent the flat annular leading surface 62 of the
bit holder to receive a similarly shaped shank portion 25 on the
bit 21 shown in FIG. 2.
[0033] In an important aspect of the present invention, a slot 81
extends through the sidewall of the shank portion from the rear
semi-annular face 77 to a rounded front slot termination 82. An
interference fit between the outside of tapered shank portion 73
and the like tapered bore 80 of the bit block 61 is greater than
the interference fit possible if slot 81 was not in the shank
portion. For example, a 1-1/2 inch diameter shank without a slot
would ordinarily have about 0.001-0.003 inch interference. With
slot 81, the same size shank may have about 0.005-012 inch
interference in the portion including the slot 81. As the distal
end 77 of the shank portion 68 is positioned in the tapered bore 80
of bit block 61, the slot allows the now C-shaped portion of the
shank to contract its outer diameter radially to ease the insertion
of the bit holder in the bit block bore 80. This slotted portion of
the shank 81 allows the C-shaped portion of the shank to act as a
very strong radial spring, similarly to a hollow spring steel roll
pin. The portion of shank 68 forward of slot 82 provides a 360
degree radial interference fit with the bit block bore 80, and may
be greater than, equal to, or less than an interference fit at the
portion of the shank at 101. The length of the slot 81 with respect
to the length of the shank portion 68 may be varied depending upon
the application proposed for the bit, bit holder and bit block
assembly in order to optimize the operation of same. The slot 81
may, when desired, extend all the way to the rear annular flange
back side 67 of the front tapered shank portion of the bit holder
60. The longer the slot, the less spring action force of shank 68.
A smaller width slot provides a greater spring force. The taper for
the shank 73 and bore 80 is preferably 1 degree on each side, but
may be more or less, such as 2 to 4 degrees per side or 1/4 to 3/4
degree per side, if desired. The smaller taper such as 1 degree has
a longer length of interference fit engagement and produces more
radial pressure for the same axial force exerted upon it than a two
degree taper for the same press fit values.
[0034] Referring to FIGS. 5 and 6, bit block 61 is similar to bit
block 23 with the exception that the bit block bore 80 is tapered
on the order of about 1 to 4 degrees per side or 2 to 8 degrees of
included angle, unlike straight bore 49. A second locator pin 89
may be mounted in a bore 89a to extend slightly into the bore 80 of
the bit block 61. In use pin 89 is about 1/2 inch in diameter and
extends into slot 81 of the bit holder slot about {fraction (3/16)}
inch to keep the bit holder 60 from rotating in the bit block 61
and to align the slot 81 in the bit block. A clearance hole 69a on
top flat surface 85 allows the locator pin in 69 (FIG. 3) to be
positioned loosely therein. An annular slot 87 is formed across the
bottom portion of the bit block tail surface 88, otherwise, bit
block 61 is very similar to bit block 23 in construction.
[0035] Referring to FIGS. 7 and 8, the bit 21 and the second
embodiments of the bit holder 60 and bit block 61 are shown in
assembled condition with the exception of the modification in the
bit block 61 to provide a slot 85 positioned in the outer portion
of bit block 61 to more easily allow the insertion of tools in the
rear of the bit block 61 to drive the bit 21 from the bit holder
60.
[0036] FIG. 8 shows the bottom of the assembly including the flat
planar mounting pad 86 which mounts to the rotating wheel or moving
track on which the assembly is positioned. As one can see from
FIGS. 7 and 8 there is no bolt, retaining pin or other retaining
means to maintain the bit holder in the bit block. Additionally,
force may be applied to the distal end surface 77 of the bit holder
60 to drive the bit holder out of the bit block 61. As with the
first embodiment of the present invention, the notch 65 in the
front tapered portion of the bit holder 60 allows a chisel (not
shown) or other such device to apply force on the back side-of the
bottom flanged portion 28 of bit 21 to drive the bit out of the bit
holder. Again, no bolts, retaining pins, retaining rings or the
like are necessary between the bit holder 60 and the bit block
61.
[0037] Referring to FIGS. 9 and 10, a third embodiment of the bit
holder of the present invention, generally indicated at 90, is
similar to the second embodiment bit holder 60 with two exceptions
to be discussed below. The forward portion of the bit holder 90
including the leading flat annular surface 91, a cylindrical front
collar portion 92, the middle tapered portion 93 and the enlarged
flange portion 94 perform similar functions to the forward portion
of the bit holder of the second embodiment 60. Also, a pair of
notches 95, 96 perform an identical function to the notches 64, 65
of the second embodiment. The forward portion of the bit holder of
the third embodiment is somewhat more compact axially than the
second embodiment. Another difference in the third embodiment of
the present invention is the construction of the shank portion,
generally indicated at 97.
[0038] The shank portion 100 is also tapered as is the shank
portion 68 in FIG. 3 with approximately 1 degree of taper per side
as shown at T.sub.1 in FIG. 9. The shank portion also includes an
undercut section 98 between the back side 94b of the enlarged
flange portion and the shank portion 97 to avoid sharp areas of
stress when mounting the bit holder 90 in a bit block such as that
shown at 61. This portion of the shank could also be designed in
either embodiment using a radius at 98 and providing sufficient
relief at countersink 120 (FIG. 5) in bit block 61. In an important
aspect of the third embodiment of the present invention, the
tapered outermost surface of the shank is divided into a front
tapered portion 100 and a rear tapered portion 101. In this third
embodiment 90, shoulder 102 is formed between the front tapered
portion 100 and the rear tapered portion 101. The distal portion of
the shank 77 (FIG. 7) is constructed identically to that of the
second embodiment with a rear face 103 a distal chamfer 104 a
cylindrical tail portion 105, a transition chamfer 106 and rear
tapered portion 101. Likewise, the bit holder of the third
embodiment may include a central bore 107 therethrough and a
slotted portion 108 (FIG. 10) similar to the slot 81 (FIG. 3) of
the second embodiment 60. Slot 108 allows for a greater
interference fit between rear taper 101 and bit block bore 80 (FIG.
5). In the third embodiment 90, the shoulder 102 reduces the
interference fit on opposing sides from about 0.009 at 101 to about
0.002 inch between the frontal portion of slot 108 and undercut 98.
The rear taper 101 and the front taper 100 are preferably
identical, in this embodiment 1 degree. However, these tapers can
vary as discussed previously above.
[0039] Identical smaller tapers give a longer taper contact at each
end of the shank. If the angle of the taper at portion 100 is
greater than the angle of the taper at portion 101, the axial
length of contact between taper portion 100 and bore 80 of block 61
will be lessened. Also, a convex surface may be substituted for the
tapers 100 and 101 with the result being less surface contact
between the holder shank 100, 101 and block bore 80.
[0040] The shoulder 102 assures that the portion of the front taper
100 immediately adjacent the shoulder 102 does not touch the bore
80 of the bit block 61 as the bit holder is driven into the bit
block. As the bit holder is further driven into the bit block and
the diameter of front taper 100 increases until interference
contact is made adjacent the forward end of taper 100 where the 100
percent circumferential surface is located The slot 108 decreases
in width mostly in press fit zone 101 to allow the bit holder to be
driven into the bit block. The position at which the front taper
100 achieves an interference fit with the bit block bore 80 is
approximately that position shown in FIG. 11, i.e., about 1/4 to
5/8 inch. The interference fit between the taper portions 100-101
and bore 80 maintain the bit holder in fixed mounted position in
bore 80. The use of pin 89 which extends through bore 89a into the
bore 80 (and slot 108 when the holder is inserted in the block)
assures that proper alignment and minimal rotation occurs between
the holder 90 and the bit block 61. However, when using greater
interference fit on taper portion 101, no pin may be required in
certain applications.
[0041] Referring to FIGS. 11 and 11a, a means for mounting the bit
holders of the present invention in their respective bit blocks is
shown at FIG. 11, and a means for demounting or removing the bit
holders from their respective bit blocks is shown at FIG. 11a. In
FIG. 11, the bit holder 90 or bit holder 60 are substantially
driven into the bit block 61 with the use of a first drive pin,
generally indicated at 105, that includes an elongate shank portion
106 having a slip fitting cylindrical distal end 120 which loosely
fits in the bore 107 (FIG. 10) of the bit holder. A reduced shaft
portion 121 may be positioned mediate the distal slip fitting
cylindrical portion 120 and an enlarged cylindrical portion stop
member 122 including an annular face 123 thereon adapted to
matingly engage the front annular flat surface 91 of the bit
holder. An enlarged head portion 117 absorbs the blows of a hammer
118, which strikes the same to drive the press fit shank portion 97
(FIG. 9) of the bit holder 90 into the bore 80 of the bit block 61.
The slip fitting distal cylindrical portion 120 and the annular
face 123 of the drive pin 105 assures that the bit holder 90 will
be accurately positioned to drive same into the bore 80 of the bit
block 61 without harming any potential annular inserts, such as
shown at 163 in FIG. 12 positioned at the upper flat annular
surfaces of either the bit holder or the bit block. The hardened
inserts, being more brittle than the softer ductile material of the
remainder of the bit block 61 and bit holder 90 will be more likely
to be damaged during insertion of the bit holder 90 in the bit
block 61 if a non-close fitting drive pin were used rather than the
preferred embodiment drive pin 105.
[0042] Referring to FIG. 11a, a second drive pin, generally
indicated at 130, is utilized to remove or drive out the bit holder
90, or bit holder 60 of the present invention from the bit block
61. Drive pin 130 includes an enlarged head portion 131 for
accepting the blows of the hammer 118 previously mentioned. The
shaft portion 132 includes a slightly reduced diameter distal end
133 having a semispherical tip 134 of larger diameter than the bore
107 of the bit holder 90.
[0043] In operation, the semispherical distal tip 134 is positioned
on the central bore 107 of the bit holder 90 at a countersink 77a
(FIG. 7) on its rearward distal end 103. Since the semispherical
end 134 is larger in diameter than the central bore 107, it allows
the drive pin 130 to be positioned in other than a coaxial position
with the central bore 107 of the bit holder 90. Countersink 77a
provides for additional engagement between the distal end of the
tool 130 and the bit holder. This provides positioning the drive
pin around combinations of bit, bit holders and bit blocks mounted
adjacent the bit holder that is being removed from its respective
bit block. The hammer 118 striking the enlarged end 131 of the
drive pin provides an axially oriented component of force to drive
the press fit bit holder 90 outwardly of the bore 80 of the bit
block 61. When needed an anti-seize grease is applied to the mating
parts for easier assembly and disassembly.
[0044] Referring to FIG. 12, a second means of inserting the bit
holder 160 into the bit block 61 is shown. This second insertion
means includes a threaded bolt, generally indicated at 110,
including a threaded portion 111, which extends through the bore
180 of the bit holder 160 and out the distal end thereof. A
specialized nut 112 is threaded on the threaded distal end of the
bolt 110 until contact is made with the rear of the bit block.
Then, nut 112 is retained in a non-rotating position by a wrench or
by means between the nut and the back side slot 115 of the bit
block 61. Then the hexagonal front bolt portion 113 of the bolt is
rotated with the threads 111 engaging the internal threads on the
nut 112 such that the hex head 113 drives the front face 162 of the
bit holder, and thus the remainder of the bit holder 160, into the
bit block 61 until the back side annular flange 67 (FIG. 3) seats
on the front face 85 of the bit block 61. The front face 162 of bit
holder 160 includes a hardened frustoconical tungsten carbide
insert 163 disclosed in U.S. patent application Ser. No.
09/121,726.
[0045] While four embodiments of the present invention have been
shown and described, it will be apparent to those skilled in the
art that changes and modifications may be made without departing
from the true spirit and scope of the present invention. It is the
intent of the appended claims to cover all such changes and
modifications which fall within the true spirit and scope of the
invention.
* * * * *