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Патент USA US2079787

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May 11, 1937~
H. w. H. BETH
Filed Aug. 12, 1936
‘ VA
w a
Hugo ' W H. BETH
Patented May 11, 1937
Hugo W. H. Beth, Worcester, Mass, assignor to
Norton Company, Worcester, Mass., a corpora
tion of Massachusetts
Application August 12, 1936, Serial No. 95,503
4 Claims.
(Cl. 51-207)
The invention relates to pulpstones.
One object of the invention is to provide an
improvement in the type of pulpstone disclosed
in United States Letters Patent Reissue No.
5‘ 19,678 to R. C. Benner and H. E. Stowell. An
other object of the invention is to avoid frac
turing of the sectors of a pulpstone by reason
of differential thermal expansion thereof. An
other object of the invention is to provide an ef
10 ?cient construction for a pulpstone.
Other ob
jects will be in part obvious or in part pointed
out hereinafter.
The invention accordingly consists in the fea
tures of construction, combinations of elements,
and arrangements of parts, as will be exempli?ed
in the structure to be hereinafter described and
the scope of the application of which will. be
pointed out in the following claims.
In, the accompanying drawing, the single fig
ure thereof represents an axial sectional View of
one-half of a pulpstone constructed in accordance
with the invention, together with the mounting
shaft and ?anges.
In the illustrative embodiment of the inven
25 tion I provide a pulpstone construction which,
with the exception of the feature to be speci?cal
ly pointed out hereinafter, may be substantially
the same as that disclosed in the Reissue Pat
ent No. 19,678 to Benner and Stowell above re
30 ferred to. For example, I may provide an outer
body or annulus l of abrasive annuli 2 each one
of which comprises a plurality of sectors. I may
further provide an inner portion 3 of concrete or
other material as disclosed in the aforesaid Ben
35 nor and Stowell patent. I may further provide
driving ?anges 5 in threaded engagement with
a driving shaft 6 and I may provide a pair of
metal facings ill.
I may further provide reinforcing rings or
40 hoops 8 such as disclosed in U. 8. Letters Patent
to Bonner and Soley No. 1,975,970. ‘These may
be surrounded with material 9 of any of the
formulae disclosed in the patent last above iden
ti?ed- I may use any other features in either of
45 the two- patents mentioned not inconsistent with
each other, and the accompanying drawing clear
ly discloses the illustrative embodiment of this
invention so far as constructional features are
Pulpstones constructed in accordance with the
patents above identi?ed have been found in ac
tual practice frequently to fail in service by the
fracturing of one or more end sectors of the
annuli identi?ed in the accompanying drawing
the references 2a. I have found that this oc
curs despite careful balancing or attempts at bal
ancing coei?cients of expansion, for the reason
that some portion of the abrasive annulus I is
rigidly held between the ?anges 5, 5 while the
outer portion of the abrasive annulus l is free
to expand, and moreover the heat generated dur
ing grinding is generated at the periphery of the
wheel and there is, during grinding, a thermal
differential in the annulus I from the peripheral
outside to the inner portion. It is probably true 1H 0
that no metal parts of the shape of the ?anges
5 can resist a direct thrust due to thermal ex
pansion. Nevertheless,\ the pressure of the
flanges 5 is a factor inso- much as axial expan
sion of the outer portion of the annulus ‘I
would otherwise force axial ‘expansion of the
inner portion, even though cold, by reason of
the integral connection. While the ?anges 5,
5 might not be able to resist a direct thrust from
thermal axial expansion of the inner portion of 20
the abrasive annulus I, they can resist axial ex
pansion of this inner portion of the annulus (in
side the rings 8) by reason of thermal expansion
of the outside portion of the annulus (outside of
the rings 8) because this force can be no greater 25
than the shearing strength of the abrasive annuli
which is weakened at what I term the throats, H.
As partly explained .in the patents referred
to, there is great force exerted by the ?anges 5
upon the pulpstone in an axial direction. This is 30
due to the right and left~hand threads on the
shaft 6 which are so disposed, with relation to the
direction of rotation, that rotation of the pulp
stone and consequent resistance due to grind
ing at the periphery tends to tighten the ?anges 3
5. A pulpstone may, when it is started up, be
quite cold. As it is started, the full load is
placed upon the annulus l and this tends to tight
en the flanges 5 on the, shaft 6, the shaft 6 being
at that time cold. The periphery of the annulus
I heats up ?rst and becomes quite hot even down
to the rings 8 while the rest of the stone, includ
ing the flanges 5 and the shaft 6, may still be
quite cold. It will be understood that condi
tions met with in practice vary considerably and 45
the foregoing is a conservative statement of what
happens when a pulpstone is started and, for
one reason or another, the water gives out soon
after the start of the grinding operation. Under
such conditions, temperatures way above the boil- 50
ing point of water may be reached and trans
mitted to the entire outer portion of the an
nulus i.
As the annuli 2 and 2a, are heated, those annuli
at the center or near the center do not ?rst frac- 55
ture, as the pressure is more or less the same on
both sides. The worst condition is met with at
the annuli 2a. and, therefore, in actual practice,
these are usually the ?rst to go.
It will be seen
5 that the annuli 20., so far as the outer portion
outside of the rings 8 is concerned, are absolutely
unsupported, on the outside (in an axial direc
tion) , while from the inside (in an axial direc—
tion) they are subjected to the sum of the ex
l0 pansions due to the coei?oient of expansion of
the material times the number of degrees of tem
perature differential times the axial length of
the annulus 1 inside the outside annuli 2a. As
these same annuli 2a are rigidly held inside of
15 the rings 8, a leverage is produced which fre
quently fractures them.
I correct this condition by providing com~
pressible ?llers I2. Preferably I use a material
different from that disclosed for the embedding
20 material 9 in Patent No. 1,975,070. This ?ller
material I2 need not have any function so far
as holding the sectors together in an axial direc
tion is concerned. This function is sufficiently
achieved by the construction otherwise disclosed
25 and disclosed in the patents referred to. While
it is suf?cient, so far as conditions usually met
with in practice are concerned, to provide ?llers
I2 which have the shape of annular disks, or
Other materials for the ?llers I2 and I3 may
be used. For example, a Babbitt metal ?ller with
compressible posts made according to the disclo
sure of United States Letters Patent No. 1,815,108
to Larsson may be substituted. The function of
the ?llers I2 and I3 is to deform under pressure,
whether or not these ?llers return to their in
itial condition after the particular stress or strain
has been relieved and the stone returns to a
state of thermal equilibrium.
In the drawing I have shown the ?anges 5 and
the metal facings I0 as slightly larger in diameter
than in the reissue patent to Benner and Sto
well above referred to in so much as, due to the
provision of the compressible ?llers I2 and I3, the 15
?anges 5 may be extended outwardly and by do
ing. so differential strains if the heat ever pene
trates to the interior portion of the annulus I
are better avoided. By extending the metal
parts further outwardly, a directthrust which 20
will deform the metal is achieved by the thermal
expansion and this to some extent reduces what
I term the leverage effect of the expansion.
This leverage effect is due to holding the material
at the inside and providing a condition where 25
thermal expansion creates a turning couple at
the outside of the annulus.
There is a certain
resiliency to the material 9 which su?iciently
' sectors thereof, I may also provide ?llers be
overcomes the leverage effect so that the con
30 tween sector blocks in a circumferential direc
tion, as indicated by the reference character I3
at" the central portion of the annulus I. The
Single ?gure will be understood to be an axial
struction illustrated in the drawing ful?lls prac
sectional view of the embodiment of the inven
tion in which both types of ?llers are used, dis
closing ?llers I3 which extend in axial planes
at the central portion of the drawing, the section
plane being broken. In the preferred embodi
ment of the invention both the annular ?llers I2
40 and the axial ?llers I3 will be provided, but so
far as certain features of the invention are con
cerned and under certain conditions of operation
only the ?llers I2 will be used.
It will be understood that so far as practical
45 requirements are concerned, it is sufficient to
safeguard the pulpstone against certain stresses
and expansions without safeguarding it against
all. In fact, considering each abrasive sector
as a unit, if the outer portion be heated up and
50 the inner portion be not heated, there is a cer
tain strain set up in the sector itself which no
amount of mechanical device outside of the sec
torlpossibly could completely overcome. Never
theless, abrasive material is suf?ciently elastic
55 to withstand a certain amount of such strain.
It is the unsupported and multiplied strain and
stress due to di?erential expansion as herein
above explained which this invention relieves.
Considering now the material for the ?llers I2
60 and I3,.I prefer to use a compressible and de
formable composition. One example of a com
position which might be used is as follows:
Percent by weight
Rubber _______________________________ __ 45.6
65 Sulphur
______________________________ __ 24.6
80 grit size silicon carbide _____________ __ 4.8
16 grit size cork _______________________ __ 25.0
The above formula may be widely varied. For
70 example, the following may be used:
Parts by weight
________________________________ __ 5O
Sulphur ________________________________ __ 27
Silicon carbide __________________________ __ 23
____________________________ ___ ____ __ 44}
tical requirements. However, so far as many fea
tures of the invention are concerned, the flanges
5 have the same relation to the abrasive an
nulus I as is disclosed in the aforesaid patent to
Benner and Stowell.
The joints into which the ?llers I2 and I3 are
placed may be of the order of a quarter of an inch
wide. With the use of a different ?ller material,
spaces of different width may be provided. I
may provide abrasive segments of zigzag con
tour in developed view, as disclosed in U. S. Let
ters Patent No. 1,469,723 to Greenwood, but on
the other hand due to the narrowness of the ?llers
I2 and the fact that there is some abrasive grain
in the composition, the faces of the sectors may
be in radial planes perpendicular to the axis.
Considering now the manufacture of the en
tire pulpstone, it may be assembled according to
previous practice, laying the ?ller material I2
and I3 in position as the sectors are assembled.
Then by means of a single heat treating opera
tion, the ?llers I2 and I3 as well as the material 9
may be vulcanized, and at this same time other
material which is thermally set in accordance
with the disclosure of the patents to Benner and 55
Stowell and Benner and Soley may be heat treat
ed. Other procedures currently in use or which
may be adapted to the circumstances may be em
ployed in the assembly and construction of the
It will thus be seen that there has been pro
vided by this invention an article in which the
various objects hereinabove set forth together
with many thoroughly practical advantages are
successfully achieved. As many possible em 65
bodiments may be made of the above invention
and as many changes might be made in the em
bodiment above set forth, it is to be understood
that all matter hereinbefore set forth or shown
in the accompanying drawing is to be interpreted 70
as illustrative and not in a limiting sense.
I claim:—
1. In a pulpstone construction, a shaft having
right and left-hand threads, ?anges mounted on .
the shaft in threaded engagement with said
threads, an inner portion to the stone extending
around the shaft and radially smaller than the
?anges so that the pressure of the ?anges may be
exerted beyond the inner portion, sectors ar
ranged in the form of an annulus and around the
inner portion, reinforcing rings embedded in the
sectors, the sectors abutting each other in an
axial direction inside of the rings and at that
portion receiving the thrust of the ?anges, and
10 ?llers of material which Will deform under pres
sure between the sectors, from end to end of the
stone, outside of the rings.
2. In a pulpstone construction, a central sup
port, a series of abrasive annuli each comprising
15 a plurality of sectors mounted on said support,
inner portions of said sectors being in abutting
engagement axially, and outer portions of said
sectors being spaced, and compressible ?llers be
tween said outer portions.
3. In a pulpstone, a central support, a series of
abrasive annuli on said support, each annulus
comprising a plurality of separate blocks, each
block being in part at least substantially a sec
tor and each block being wider in an axial direc
tion at the inside adjacent the support than at the
outside adjacent the periphery, means holding the
blocks together axially, and means holding the
blocks on the support radially.
4. In a pulpstone, a central concrete support, 10
a series of annuli of abrasive blocks on said sup
port together forming an abrasive annulus, each
of the series comprising substantially sectoral
blocks, and metal rings between individual an
nuli of the series of annuli, the blocks being in
non-compressible relation inside the rings, and
the blocks being spaced outside the rings.
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