Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
This invention i~ related to the field of earth-
working tools such as those used on machines for cutking
rock or coal or machines for road building and road
maintenance. For purposes of illustration, this inven-
tion will be shown and described with respect to a road
planer, a particular type of road building and road
maintenance equipment.
The tools with which this invention is most
concerned are those tools comprised of a base, a block
(sometimes called a lug~, and a bit for contacting the
working medium. The bit may be any one of several types
which are well known in the prior art.
A normal conseyuence of utilizing tools is an
abrasive working medium such as the earth i8 that the
tools wear out and must then be replaced. The period of
time during replacement is greater when the bits are
tipped with a hard wear resistant material such as
tungsten carbide.
The tools are attached to a rotor ~which rotates
causing the bits to dig into the earth. Often, the base
and block are welded to the rotor while the bit is
removably attached to the block. In normal operation t
only the bit has to be replaced. However, it is recog-
nized that the block itself may also wear out or even
break. In this circumstance, the whole machine must be
shut down so that a welder may be located for the
purpose of removing the old block and then installing a
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new one. There is considerable expense involved in
allowing such an expensive machine to lay idle.
Thus, it is desirable to also make the block
replaceable as is, for example, shown in United States
Patent NosO 2,905,456; 3,820~84~7 and 4/180,292~
This only partially solves the problem since~ if an
underground obstacle is encountered, such as buried
railroad tracks, manhole rings, expansion plates or deck
plates on bridges/ an abnormally high cutting load will
be put on the bit, and the base itself may be ripped
from the rotor. If this occurs, the machine will then
have to be shut down and a welder will have to be
located as before.
A way to remedy the situation is to make the base
and block sufficiently massive so that, together, they
can withstand the resultant cutting forces. This is
shown, for example, in United States Patent No.
3,749,449. A consequence of this design is that the
rotor becomes very heavy due to the "beefed-up" base and
block so that the force available for cutting action
through the bit is somewhat reduced. Of course, such a
design would also he more expensive.
An alternative to the problems of the prior art has
been provided by the invention of this application.
Thus, it is an object of this invention to provide
a hase and block assembly that is both lightweight and
durable.
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It is another ob~ect that the base and block
assembly be cost effective.
It is a further object that the block of a base and
block assembly be replaceable and yet be rigidly held by
the base when in operation.
It iS a still further object of this invention that
the base of a base and block assembly be protected from
abnormally high cutting loads.
BRIEF SUMMARY OF THE lNVh~N~l~ION
According to the present invention, disclosed is an
assembly for use with an earthworking bito There is a
base and a block engaged in the base. I'he block has a
shank portion and a toolholder portion. The toolholder
portion extends from a first end of the shank and is
adapted for receiving an earthworking bit. There is
also means for causing the block to preferentially fail
when exposed to abnormally high cutting loads.
The base has a T-shaped recess formed by the inter-
section of a vertical slot and a horizontal slot. The
block has a T-shaped portion extending from a second end
of the shank portion. When Eully assembled, the
T-shaped portion slidably engages the T-shaped recess~
The failure means is disposed on the shank portion
and, preferably, it is on the shank portion between the
toolholder portion and the T-shaped portion~ Pre~er-
ably, also, the failure means comprises a segment of
said shank portion in which the cross section is reduced
from the remainder of the shank portion. Most
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preferably, the reduced cross section area segment com-
prises a groove situated along at least one peripheral
surface of the shank portion.
The base also has a top portion of two intersecting
surfacesO Each of the top portion surfaces is inclined
to the horizontal. The block also has a bottom portion
of two lntersecting surfaces e~tending outwardly from
the first end of the shank portion. Each of the bottom
portion surfaces is inclined to the horizontal. The top
portion surfaces of the base directly oppose the bottom
portion surfaces of the block when the block engages the
base. Preferably, the angle that each of the top por-
tion suraces of the base and the angle that each of the
bottom portion surfaces of the block makes with the
horizontal is about 10 degrees.
Even more preferably, the horizontal slot and the
top portion surfaces of the base diverge from one
another toward the rear of the base. The T-shaped
portion and the bottom portion surfaces of the block
diverge in a similar manner from one another toward the
rear of the block. The base and the block become
wedgingly engaged due to this divergence as the block
moves rearwardly in the base.
Also, according to the invention, the base and
block assembly preferably comprise means for re~aining
the block in the base in immovable engagement. Preer-
ably, the retaining means comprise fasteniny means~ a
threaded recess in the rear of the shank portion and a
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perforation in the rear of the T~shaped recessO The
perforation and threaded recess are in alignment when
the hlock engages the base. The fastening means passes
through the perforation and engages the threaded
recessO
According to the invention, a block is disclosed
for use with an eartbworking bit. There is a shank por-
tion and a toolholder portion extending from a first end
of the shank and adapted for receiving the earthworking
bit. There are also means for causing the block to
preferentially fail when exposed to abnormally high
cutting loads~
Preferably, the block also has a T-shaped portion
extending from a second end oE the shank portion.
Preferably, also, the failure means is disposed on
the shank portion. More preferably, it is on the shank
portion between the toolholder portion and the T-shaped
portion. The ~ailure means comprises a segment of the
shank portion in which the cross section area is reduced
from the remainder of the shank portion. It is most
preferable that the reduced cross section area segment
comprises a groove situated along at least one peri-
pheral surface of the shan~ portion.
The bloc~ also has a bottom portion of two inter-
secting surfaces extending outwardly from the first end
of the shank portion. Each of the bottom portion
surfaces is inclined to the horizontal. Preferably, the
angle that each of the bottom portion surfaces makes
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with the horizontal is about 10 degreesO Preferably,
~he T-shaped portion and bottom portion surfaces diverge
from one another to~ard the rear of the block.
According to the invention, there is also disclosed
a method to protect the base of a base and block
assembly when used with an earthworking bit. The method
comprises preferentially weakening the block so as to
cause the block to fail when exposed to abnormally high
cutting loads and engaging the block with the base.
Preferably, the step of preferentially weakening is by
reducing the cross section area of a portion of the
block. Most preferably, the step of reducing the cross
section area is by forming a groove along at least one
peripheral surface of the hlock~
BRIEF DESCRIPTION OF THE DRAWINGS
The exact nature of the present invention will
become more clearly apparent upon reference to the
following detailed specification taken in connection
with the acco~panying drawings in whichs
Figure 1 is a perspective view of a bit and block
assembly on a rotor.
Figure 2 is a Eront view of a base and block
assembly with an earthworking bit.
Figure 3 is a side view of a base and block
assembly with an earthworking bit.
Figure 4 is a side view of the block.
Figure 5 is a front view of the block.
Figure 6 is a rear view of the block.
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Figure 7 is a Eront view of the base.
Fi~ure 8 is a side view of the base.
DETAILED DESCRIPTION OF T~E INVENTION
Referring to the drawings in more detail, Figure 1
shows the base 2 and the block 4 as it would normally
appear on the rotor 6. As can be seen, the base is
welded S to the rotor.
Figures 2 and 3 show the base 2 and the block 4
with an earthworking bit 10. The bit shown is a
rotatable bit with a captive keeper, but may be any one
of several types which are well known in the prior art.
The section of the base in Figure 3 is illustrative of
the engagement of the base, block and fastening means.
Referring now additionally to Figures 4 through 8,
there is disclosed according to the invention an
assembly for use with an earthworking bit. There is a
base 2 and a block 4 engaging the base. The block has a
shank portion 12 and a toolholder portion 14 extending
from a first end 16 of the shank and adapted for
receiving an earthworking bit 10. There are also means
for causing the block to pre~erentially fail when
exposed to abnormally high cutting loads.
The base has a T-shaped recess 18 formed by the
intersection of a vertical slot 20 and a horizontal slot
22. The block has a T-shaped portion 24 extending from
a second end 26 of the shank portion. The T-shaped
portion slidably engages the T-shaped recess.
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Preferably, the failure means is disposed on the
shank portion. More preferably, the failure means may
also be disposed on the shank portion between the tool-
holder portion and the ~-shaped portion. The failure
means comprises a segment of the shank portion in which
the cross section is reduced from the remainder of the
shank portion. Most preferably, the reduced cross
section area segment comprises a groove 28 situated
along at least one peripheral surface of the shank
portion.
It is necessary so as to fulfill the objectives of
the invention that the groove be located along at least
one peripheral surface; ho~7ever, it is contemplated
within the scope of the invention that the yroove may
also be located on two, three or all of the peripheral
surfaces of the shank portion~
Similar designs, such as any thinning of the cross
section of the shank, are al90 contemplated within the
scope of this invention.
The base may also have a top portion of two inter-
secting surfaces 30. Each of the top portion surfaces
i5 inclined to the horizontal 32. The block also has a
bottom portion of two intersecting surfaces 34 extending
outwardly from the first end 16 of the shank portion.
Each of the bottom portion surfaces is inclined to the
horizontal 36, The top portion surfaces 30 of the base
directly oppose the bottom portion surfaces 34 of the
block when the block engages the base.
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This can best be seen in Figure 2 where the top
portion surfaces oppose the bottom portion surfaces at
38. The purpose of inclining the bottom portion
surfaces and the top portion surfaces is to counteract
side loading of the earthworking bit.
It is preferable that the angle 40 that each of the
top portion surfaces of the base and the angle ~0 that
each of the bottom portion surfaces of the block makes
with the horizontal is about lO degrees.
Preferably, the horizontal slot 22 and the top por-
tion surfaces 30 of the base diverge from one another
toward the rear 42 of the base~ The T-shaped portions
24 and the bottom portion surfaces 34 of the block
diverge in a similar manner from one another toward the
rear 4~ of the block. The base and block be~ome
wedgingly engaged due to this divergence as the block
moves rearwardly in the base.
Also, according to the invention, there are means
for retaining the base and block in immovable engage-
ment. It is desirable to retain the base and block inimmovable engagement so as to avoid unnecessary wear
between the base and the block.
Preferably, the retaining means comprise a fasten-
ing means, a threaded recess 48 in the rear 44 of the
shank portion and a perforation 50 in the rear 42 of the
T-shaped recess 18. The perforation 50 and the threaded
recess 48 are in alignment when the block engages the
base. ~he fastening means passes through the perfora-
tion and engages the threaded recess.
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The fastening means is preEerably a bolt 46 and
lock washer 47 as shown in Figure 3. However, similar
fastening means such as a bolt and spring are also
contemplated within the scope of this invention.
According to the invention, disclosed is a block 4
for use with an earthworking bit 10. There is a shank
portion 12 and a toolholder portion 14 extending from a
first end 16 of the shank and adapted for receiving an
earthworking bit 10. There are also means for causing
the block to preferentially fail when exposed to abnor-
mally high cutting loads. The block also has a T-shaped
portion 24 extending from a second end 26 of the shank
portion.
Preferably, the failure means is disposed on the
shank portion, or even more preferably, is disposed on
the shank portion between the toolholder portion and the
T-shaped portion. The failure means comprises a segment
of the shank portion in which the cross section area is
reduced from the remainder of the shank portion. Most
preferably, the reduced cross section area segment com~
prises a groove 28 situated along at least one peri-
pheral surface of the shank portion.
While a groove is particularly shown and described,
any similar feature that causes the cross section of the
shank portion to be reduced in area is contemplated
within the scope of the invention.
The block has a bottom portion of two intersecting
surfaces 34 extending outwardly from the firsk end 16
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of the shank portion~ Each of the bottom portion sur-
faces is inclined to the horizontal 36. The purpose o~
inclining the surface is to counteract the side loading
of the earthworking bit. Preferablyl the angle 40 that
each of the bottom portion surfaces makes with the
horizontal is about 10 degrees.
Preferably, also, the hlock has a T-shaped portion
24 and bottom portion surfaces 34 diverging from one
another toward the rear 44 of the block.
According to the invention, disclosed i5 a method
to protect the base of a base and block assembly when
used with an earthworking bit. The method comprises
preferentially weakening the block so as to cause the
block to fail when exposed to abnormally high cutting
loads and engaging the block with the base.
It is anticipated that this method will cause the
block to fail first when exposed to abnormally high
cutting loads, or at least to deform so as to preclude
further service, thereby preventing the base from being
ripped off the rotor.
Preferably, the step of preferentially weakening
comprises reducing the cross section area of a portion
of said block. Most preEerably, the step of reducing
the cross section area comprises forming a groove 28
along at least one peripheral surface of the block.
While a groove is particularly shown and described as
the most preferred method of preferentially weakening,
similar designs which cause the cross section oE the
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block to be reduced in area are contemplated within the
scope of the invention.
Modifications may be made within the scop.e of the
appended clai~s.
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