Note: Descriptions are shown in the official language in which they were submitted.
~ his invention relates to a segment-shaped blade
for use in a rotatable cyli~drical tool ~or machlning
elastic material, particularly pneumatic rubber tyres
for vehicles, comprising pointed triangular teeth, which
are provided on a convex outer edge and are staggered and
divided by radial cuts.
German Patent Specification 1,1659843 discloses
such a blade? in which said radial cuts extend below the
roots o~ the teeth so that the latter are M-shaped and
ha~e double prongs an~ a strong root~ ~his is intended
to ensure that a breaking out of individual teeth is
prevented with high safety. Another blade known from
that patent speci~ication has triangular teethg which
are not slit but are laterally bent to di~ferent sides
o~ the blade in alternation.
~ yre rasps provided with the known blades
having M-shaped or triangular teeth are thus available
~`or roughe~ing the rubber covering of worn vehicle t~res
~o be retreaded. ~hereas the set teeth can engage the tyre
in a ver~ large width so that the surface o~ the tyre can
be e~fecti~ely roughened~ these teeth can ~e u~ed to
provide only a very coarse roughened pattern.
It is known to use also roughening members
set with needles to roughen the side walls o~ a pneumatic
tyre which is to be retreaded~ To ensure that the cords
lying on the side walls o~ the tyre only under a thin
rubber layer will not be damaged~ it is known to use
tools provided with wire brushes. Whereas such tools
ensure a fine roughening o~ -the rubber layer9 they cannot
always be used to full ad~antage because the bristles are
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bent down after a relatively short time. An unusually strong
development of heat has even resulted ln a burning of the
tyre.
~ inally~ steel discs provided with tungsten
carbide splinters anchored at the periphery of the disc
have also been used to roughen the side walls of tyres~
In that case, a high contact pressure is required and
gives rise to an undesirably high operating temperature.
It is an object of the invention so to design
- 10 the blade which has been described first hereinbefore
that its teeth can be used like the k~own wire brushes
for a fine roughening of the rubber layer on the side
walls of a pneumatic tyre whereas a high operating tem-
perature can be avoided. In -the blade described, that
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object is accomplished according to the inven1tion primarily
in that each radial cut extends only as far as to the root
of the tooth con ~rned and that each triangular tooth is
divided b~ one or more radial cuts into at least two
triangular tooth portions which have pointed tips that
are much more slender than the pointed tip o~ the original
tooth.
Because the radial cuts in the trian~ular teeth
of such blade extend o~ly as far as to the roots of the
teeth, each tooth has at least two tooth portions7 the
pointed -tips of which when used to roughen the surface
of the rubber tyre act like the above-mentioned needles
and brushes ~o that the resulting roughened pa-ttern is
fine and particularly favourable for the vulcanization
of the raw tread to be appliedl Nevertheless, the opera-ting
temperature remains so low that the previously feared
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; burning is entirely avoidedO
Another advantage of the blade according to the
invention resides in its relatively lo~g edge li~e. ~hi~
is due to the fact that the tooth portions resulting ~rom
the radial cuts are much more pointed than the known
triangular teath so that the~ can be worn to much larger
depth because they are smaller in cross-section. ~inally,
the blade according to the invention has virtually a double
working capacity because it has at least twice the number o~
pointed tooth tips o~ the conventional blade.
In a preferred embodiment of the invention, the
tooth portions of a tooth are equal in size and are bent
out of the plane of the blade to different sides, in known
manner, or one tooth portion lies in the pl~ne o~ the blade
and the other tooth portion is ~ent out of the plane of -the
blade. Qbviously, the manufacture of such blades is not more
complicated than the manufa¢ture of blades having wide
; triangular teeth because the incLividual teeth can be
divided by an ordina~y cutting tool and it is not necessary
to bend all tooth portions out of the plane of the blade.
~` ~lso in a preferred embodiment o~ ths invention,
a wide-root triangular tooth is provided with one or two
radial cu~s before and behind its pointed tip~ the long
middle tooth portion is offset to one side o~ the plane
o~ the blade, the short other tooth portions are bent to
the other side of the plane of the blade or lie in the
plane o~ the blade, and all tooth points terminate pre- -
~erably in an imaginary arcuate plane. In a wide-root
triangular tooth divided into three tooth portions,
the stronger middle tooth pcrtion has the strongest
action to remove material and the two o-ther tooth portions9
which are weaker, ensure a particularly ~ine roughening of
the rubber material to be machined. If a tooth is divided
into more parts, i.eO; into four or five tooth portions,
the blade will act like a wire brush in tha-t the rubber
layer or the tyre will be finely roughened whereas large
rubber particles will not be removed and high operating
temperatures will not arise~
Some illustrative embodiments of the invention
~ 10 are diagrammaticallg shown on the accompanying drawing,
-~ in which
~ig. 1 is a side elevation showing a co~venticnal
blade~
~ig. 2 is a sectional view taken on line II-II in
Fig. 1,
~ig. 3 a side elevation showing an embodiment o~
the blade according to the invention,
~ig. 4 a sectional view tak~n on line IV~IV in
Fig. 3,
~`ig. 5 a ~ide elevation showing another embodiment
of a blade aceording to the invention,
~ig. 6 a sectional view taken on line VI-VI in
~ig 5 and
~ig . 7 a perspective view, partly broken away7
showing the blade according to the invention as illustrated
in Fig 5.
It is apparent from ~ig. 1 -that the conventional :.
blade~ 2 are segment-shaped and on their conve~ outer edge
are provided with triangular teeth 1, which are separated
by spaces 3 50 that the spacing 4 o~ the teeth 1 is
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approximately as large as the height 5 of the teeth.
~s is shown in ~ig, 29 the teeth 1 of blade 2 are bent
out of the plane of the blade in alternation~
~he invention ls ba~ed on the tooth shape
shown in Figs. 1 a~d 2 and in accordance with Fig. 3
teaches to divide such tooth 6 by an appro~imately radial
cut 7 into two portions 8 and 9. In acoordanoe with Fig. 4
portion 8 i8 bent to the left and portion 9 i~ bent to the
right out of the plane 10 o~ the blade~
Depending ~n the direction 13 or 14 in which the
blade is moved, the edges 11 and 12 defining the radial
: out 7 have a particularly strong action to remove material.
~hat action will be stronger in a~ case than the action o~
: the edges 15 and 16, which include an angle 18 with the
radial plane 17.
It is readily apparent ~rom Fig. 3 that owing
.~ to the division of the teeth the number of the pointed
tips o~ the teeth 6 of blade 10 is ~wice the number of
the pointed tips of the teeth 1 of blade 2 so that the
2 0 blade 10 can give twice the output in practice~
: Owing to the above-mentioned strong action of
the tooth portions 89 9 o~ the several teeth 6~ -the
pressure applied by a cylindrical to~l carrying such
blades 10 to the material being machined can be greatly
reduced so that a very ~ine roughened surface pattern
will be ob~ained on rubber material which has been machined
and the operating temperature remains so low that a burning
of the rubber ma-terial being machined will be reliably
avoided.
Besides, the comparable tooth cross-sections
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~ of the teeth 6 and 1 differ in a given haight so -that the
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~ teeth 5 of blade 10 shown in ~ig. 3 can be worn to a much
; larger depth, i.e ~ ~or a longer time, before they are blunt
and can no longer be used. As a result 9 the blade 10 has a
~- much longer life than the conventional blade 2 in Fig~ 1.
It is apparent from ~igs. 5 to 7 that each
tooth 19 of blade 20 is di~ided into three tooth portions
24, 25 7 26 by two radial cuts 22~ 23 disposed beEore and
behind the pointed tip 21 of the tooth. As is shown in
~ig. 6, the relatively thick middle tooth portion 25 is
o~set to one side of the plane 20 of the blade and the
two other tooth portion~ 24, 26, which are ~horter, are
merely bent to the other side oE the plane 20 of the
blade.
Fig. 6 shows the offset middle tooth portion 25
oE the too-th 28 as well as the middle tooth portion 33 of
the following tooth 29, which tooth portion is o~fset to
the opposite side. ~he position o~ the teeth is particularly
clearly apparent ~rom ~ig. 7, in which ~he bla~e 20 is shown
in perspecti~e. The middle tooth portion 34 of the tooth 35
is offset to the right side of the plane 20 o* the blade and
~he two tooth portions 36, 37 o~ the tooth are bent -to the
le~t side-o~ the plane 20 of the blade. ~his relationship
is inverted in the next following tooth 38, in which the
middle tooth portion 39 is offset to the left of the
pla~e 20 o~ the blade i.e~ on the side opposite to the
of~set tooth portion 34 o~ the preceding tooth 35, and
the two shorter tooth portions 40, 4~ are bent to the
right side of the p~Lane ~0 of the blade, iOe~ to the
side which is opposite to the tooth portions 36, 37 o~
tooth 35 which are bent to the left.
The invention is not restricted to the embodiments
shown by way of example. ~he tooth portions 36~ 37 and 40
41 may lie in the plane 20 of the blade or one o~ the
shorter tooth portions of each tooth may ~emain in the
plane of the blade whereas the other shorter tooth portions
~ are bent. ~'he points of all these tooth portions 34 to 41
: lie preferably in an imaginary common plane9 which is curved
; in accordance with the segment-shaped blade, so that the
:- tooth portions act at the same time. ~he middle tooth
portion of each tooth 35, 38 of the blade 20 is stronger
in most cases and removes the largest amount of material.
The two other tooth portions 36, 37, 40, 41, which are
weaker, ensure that the rubber material to be machined
will be finely roughened.
I~ the blade embodying the invention is provlded
with a triangular tooth which has a particularly wide root,
such tooth may be divided into four or five parts~ In that
case the several tooth portions are ~o o~fset or bent
relative to each other that their pointed tips lie in
a single curved plane and a single blade according to
the lnvention has pointed tooth tips e~ual in ~umber
to the bristles of the steel brushes previously empl~yed~
. As has been mentioned, a triangular tooth can be
; divided by radial cuts~ If one radial cut extends through
the point of the triangular tooth, the cuts on the left and
right of the radial eut may either be parallel thereto or
may also extend in a radial direGtion.
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