Note: Descriptions are shown in the official language in which they were submitted.
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DESCRIPTION
A CUTTING TOOL
Technical Field
The present invention relates to a cutting tool
which comprises a rotatable carrier element and a
plurality of abrasive cutting segments attached thereto.
Background Prior Art
Cutting devices which comprise circular cutting
discs to which abrasive cutting segments are attached
are known to the art. One such cut-ting disc is retailed,
for example, under the registered trademark TIGER. Each
cutting segment has the form of a substantially
parallelepipedic body made from a mixture of metal and
diamond powders. The segment has two mutually opposing
surfaces which are either curved or straight, and is
brazed to the disc, namely to its periphery, through
the intermediary of one of said surfaces. The thickness
of the segment, as seen at right angles to the
rotational direction of the disc, is slightly larger
than the thickness of the disc, in order to prevent
~ the disc from jamming or bindning in the workpiece,
- 20 and to avoid damaging the disc and/or said workpiece.
As the segment becomes worn in use, the height or
vertical extension of the segment decreases to the
l; same extent as its thickness, which often means that
- the segment cannot be utilized fully before it is
necessary to replace the segment or to scrap the disc.
In addition, it is necessary to manufacture and store
large numbers of segments of mutually different thick-
nesses in order to have available segments which will
fit cutting discs of varying thicknesses and diameters.
Cutting devices which comprise rotating tubular
drill bits to which abrasive cutting segments are
attached are also known in the art. One such drill bit
is retailed under the registered trademark PIXIE. Each
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segment has the form of a slightly curved, U-shaped
~ody incorporating, inter alia, synthetic diamonds.
The free legs of the U-shaped body and the web
connecting said legs are brazed respectively to the
tubular wall oE the drill bit and to the peripheral
side edge thereof. The most serious drawback
encountered with drill bits of this construction is
that it is necessary to manufacture and store large
numbers of mutually different seg~ents, since one
segment will fit solely a bit of given wall thickness
and a given ranse of diameters.
The US-PS 3 261 384 teaches a circular saw
blade with teeth for performing a cutting, chip
removing operation. The purpose of making the teeth
as angle segments is to balance the shear forces. Special
seatings on the saw body are required, which mustwithstand
the large forces. The leg 46 in Figs. 10 - 12 has the
sole task of centering the cutting edges on the saw
body, and do not participate in sawing. Due to its'
asymmetric shape the segment cannot be mounted on the
saw body so that said leg comes into engagement with
either side of the saw body.
The DE-PS 356 554 teaches a circular saw blade
for performing a cutting, chip removing operation with
the aid of edges on segments which are attached in
specially shaped grooves on the saw body. Two different-
ly shaped segments must be used, if they are to be
mounted on both sides of the saw body.
The SE 341 799 teaches a circular saw blade with
segment teeth for cutting, chip removing operation.
Each segment is substantially U-shaped and comprises
two or three parts, jointed mutually and to the saw
body by rivets. The radially inward legs do not engage
against the flat surface of the saw body (so as to be
worn at approximately the same rate as the other legs);
instead they are inserted in recesses at the periphery
of the saw body. For each thickness of saw body there
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i9 further required a segment with appropriately fsuited
thickness.
The DE-AS ~ 333 246 teaches a fside milling cutter
with parallelepipedic cutting bits for chip removing
operation, which are at-tached by clamping bodis~ in recesfsefs
in the milling cutter body~
The segments according to the four last-mentioned
publications all perform a chip removing cutting operation
with the aid of a epecially ground and angled cutting edge.
The segments have been given a shape enabling replacement of
worn and/or damaged segments, and provide seftting of the
cutting edges in an accurate, predetermined position.
Sum~ary of the Invention
It i9 an obv'lect of the present invention to
eliminate at least partially the drawbacks of prior art
cutting devices of the aforedescribed kind and like devicesfff
and to provide a rotating cutting device having abrasive
cutting segments which a) can be readlly manufactured and
utilized fully before needing to be replaced, b) present a
- 20 relatively large surface so as to facilitate attachment to
the carrier element of the device, c) can be used with any
carrier element thickness whatfsffoever, and d) can be fastened
to the periphery of the carrier element without need for
cooperating notches and pro~fections on the segments and
element, respectlvely.
The above ob~fect is met by thfe present invention
which provides a cutting device comprising a rotatable
carrier element; a plurality of single-piece abrafsive
cutting segments attached to the carrier element, each of
the segments having an angular crosfs-sectional shape with
first and second legs perpendicular to each other; wherein
the first leg is attaohed to -the periphery of the carrier
element; the se¢ond leg liesff solely against, and is attached
to one carrier element surfaoe ad~foining th~f periphery; both
~f~ the first leg and the sfecond leg are abrasive; the segments
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extend in the rotational direction of the carrier element;
all segments are identical; and the second leg of certain
segments is attached to one carrier element surface
adjoining the periphery while the second leg on certain
other segments is attached to the other of the mutually
! opposite carrier element surfaces adjoining the periphery,
such that the second leg projects in its entirety beyond the
outer confinement line of the carrier element at right
angles to the rotational direction thereof.
Brief Description of -the Dra~in~
Figure 1 i~ a perspective view of part of a
cutting device according to the invention, compri~ing a
cutting disc provided with abrasive cutting ~egments which
are thicker than the disc;
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Figure 2 is an end view of a cutting deviceaccording to the invention, comprising the cutting
segments of Fig. 1 attached to a thicker disc;
Figure 3 is a perspective view, in larger
scale, of one of the cutting elements illustrated in
Fig. 1 or Fig. 2, said segment being provided with a
fractural impression; and
igure 4 illustrates to the left of said
figure, and in partial cross-section, a cutting disc
~- 10 provided with a conventional cutting segment, and to
j the right of said figure, also in partial cross-section,
a cutting disc provided with a cutting segment accord-
ing to the invention.
~ Description of a Preferred Embodiment
i 15 The cutting device, shown partially in Fig. 1,
; comprises a circular steel cutting disc, or so-called
3 rondel 1, having a peripheral surface 2 broken by slots
: 3, so-called water slots, utilized to cool abrasive
cutting elements 4 attached to the rondel between
i 20 respective slots.
The cutting segments are moulded from a mixture
of metal and diamond powders. Each segment 4 has an
angular cross-sectional shape and comprises two mutually
perpendicular legs 5 and 6, which have a constant thick-
ness along the whole of their lengths. The upper and
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- lower surfaces 9 and 7 of the illustrated leg 5 and the
-~ lower surface 8 of the illustrated leg 6 are slightly
curved in the longitudinal direction, at least the radius
of curvature of the surface 7 corresponding to a mean
radius of curvature of the peripheral surfaces of those
- cutting discs, or rondels, to which the segments are
to be fitted. The remaining surfaces of the segments
are preferably planar.
The thickness or width of the leg 5 (geometric
extension a in Figs. 2 and 3) is not critical and can
be chosen to accom~odate widely varying rondel thick-
nesses. In the illustration of Fig. 1 the segments 4
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are attached to a rondel 1 which has a thickness smaller
than the geometric extension a, whereas in the
illustration of Fig. 2 the segments 4 are attached to
a rondel 11 which has a thickness equal to or greater
5 than the extension a.
The segments 4 are either brazed or glued to
~; the rondels 1 and 11. Glueing is made possible by the
; fact that a relatively wide area of each segment is
attached to respective rondels 1 and 11, namely the
surface 7 of the leg 5, which seats on the peripheral
surface 2 of the rondel, and-a surface 16 which adjoins
the surface 7 and extends at right angles thereto, said
surface 16 being attached to the planar side surface
-- of the rondel adjacent the peripheral surface 2.
I 15 In order to enable the cutting device to cut,
?: by abrasion, a workpiece with both sides of the rondel
11, and to balance the cutting device of Fig. 1 or
Fig. 2 against axially acting forces, the leg 6 of each
3 alternate segment is placed against one side of the
- 20 rondel and the leg 6 of each other segment against
the opposite side thereof, as illustrated in Figs. 1
~l and 2. If an odd number of segments is preferred, one
segment can be divided into two equal parts along the
`, serrated line 15 in Fig. 3, so as to avoid possible
r`' 25 problems with i~balance. In this case, a notch 14 can
! be made centrally on the leg 6, so as to facilitate
fracture of the segment along said line and to avoid
damage to the segment during the fracturing process.
- These segment halves are then placed adjacent one
another with their legs on respective sides of the
rondel.
j 7
~j As will be understood from the aforegoing, when
the width of the rondel is smaller than the width of
the segmer.ts 4, as with the Fig. 1 embodiment, the
side surface 12 of respective segments remote from the
leg 6 will project radially outwardly from the rondel
to a greater extent than the surfaces 13 adjacent the
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leg 6, and hence the workpiece will be cut, by
abrasion, with the surfaces 12 when brought into
abutment with the rondel. On the other hand, when
the rondel has a width greater than that of the
segments 4, as with the Fig. 2 embodiment, it is the
side surfaces 13 adjacent respective legs 6 which
protrude furthest from the rondel and which
consequently engage the workpiece to be cut.
When the segments 4 are subjected to wear, the
peripheral surfaces 9 of the segments become worn, i.e.
the segments decrease in height, more quickly than do
the segment side-surfaces with which the wor~piece is
cut, since the leg 6 of respective segments is given
a thickness and a wear-resistance commensurate with
the material to be worked. Consequently, with the
embodiment illustrated in Fig. 2, which is by far the
one most used, parts of the leg 6 will still remain
when the leg 5 has been worn right down to the
peripheral surface 2 of the rondel 1l, which prevents
the cutting disc from jamming or binding the workpiece
and/or avoids damage to the workpiece and to the
rondel. In the case of the Fig. 1 embodiment, however,
unless the rondel is excessively thick, the extension
a will decrease first by abrasion of the vertical
cutting surface 12, shown in Fig. 3, down to the plane
of the cutting surface 13, whereafter both surfaces 12,
13 are worn down to equal extents with a commensurate
decrease in the extension a. If it is desired that
wear on the vertical surface 13, or at least on the
leg 6, is less rapid than that on the vertical surface
12, the leg 6 may have incorporated therein a material
which has a greater resistance to wear than the material
in the remainder of the segment 4.
The table below illustrates the results obtained
when comparing a typical, conventional parallelepipedic
segment K with a comparable segment 4 constructed in
accordance with the invention, this comparison being
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given with reference to Fig. 4. Each of the two
segments is assumed to have a nominal height of 6 mm
and a length of 35 mm, and the leg 5 of the segment 4
according to the invention is assumed to have a height
or vertical extension of 2.5 mm.
Table
~onventional Segment 4 Sort
segment K according to
the lnvention
Total
cutting width 3.5 7.0 3.5 7.0 mm
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Cutting surface 123 245 123 123 mm2
Clearance b 0.3 0.5 0.75 0.75 mm
15 Clearance surface
Initial 420 420 508 298 mm2
Final 0 0 88 88 mm2
Segment volume 735 1470 802 801 mm3
Brazed surface or
20 glued surface 102210 158 184 mm2
i Brazed surface/
unit volume 0.14 0.14 0.20 0.23
Relative costs x y 0.0~ x 0.54 y SEK
; 25 The table makes clear the following facts, among
other things.
The cutting surface is smaller with a broad segment
according to the invention than with a corresponding
conventional segment, which may result in enabling lower
tool feed forces to be used. The clearance is greater with
the segment according to the invention, which reduces the
risk of binding or jamming. A larger clearance on the part
of the conventional segment can only be obtained at the
cost of a smaller attachment surface against the periphery
of the rondel. The clearance obtained with the segment
according to the invention prevails until the segment is
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totally worn. The segment according to the inven-tion
does not increase in volume with increasing cutting
widths, which results in lower material costs than
would otherwise be the case, and also means tha-t less
5 force is required for feeding the tool. The brazing
J or glueing surface on the segment according to the
invention is maximal in relation to the volume and
- weight of -the segment, which is important since the
segments are subjected to large centrifugal forces.
10 The 9 % higher cost of the thinner segment according
to the invention is justified by the beneficial
clearance obtained, and is compensated for by the
possibility of using a thinner rondel.
It will be understood that the present invention
, 15 is not restricted to the described and illustrated
. embodiment, and that the invention is solely limited
by the scope of the following claims.
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