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Патент USA US2121827

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June 2s;- 193s.
2,121,827
D. ROBERTS
STRIPPINCÄ
_ Filed oct. r'7, 1935
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INVENTOR,
_
Dad/ggœçbenîs
BY /M
I
ATroRNEY.
"
y' _ Patented`
` ‘2,121,827’
28,.'19'38.
.UNITED STATES2,121321"PATENT ~ OFFICE
s'rarrrmc
Dudley RobertapNew York,` N. Y.; assignor to
Rubatex Products, Inc.„New York, N. Y., a cor
poration of Delaware
Application October 7, 1935, serial No.. 43,803
3 Claims.
(c1. en_-69)
My invention relates to a novelfarticle of manu
ture and 'moreparticularlm relates to a novel
this rubber.
I
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The ingredients entering into the product are N
» t rubber composition gasket and methods of mak
ing thesame.`
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--with solid rubber >approaching the‘softness of
- mixed in approximately the following percentages
'
y by weight:
Although rubber compositions have been used
heretofore forfigasketsand thel like, these have
I Y usually ,had the defect that therubber weathers..
-Per cent
Washed ñrst grade‘pale crepe or smoked
. rubber
40-‘75
readily and soon becomes deteriorated. More
Sulphur
i'
6-30
over,” ordinary rubber also has the defect that '
.Light calcined magnesia_'..__ ___________ __ 3- 5
itv soon takes on a permanent set so that it leaves
Ground gilsonite
`
12
cracks and loses its sealing properties. Further
Lower melting bituminous substances.._l_.w
12
more, the manufacture of such rubber and its ap
Y The base ingredient of the product is the rub
plication _is complex and costly.
`
Accordingly, I have as an object of my inven--` ber which is preferably of a pale crepe grade #1,
' 15» tion to provide a novel gasket` structure and’ ' obtained- in sheets about gk" to 115" x10" x 20". 15
I 1
method of making the same.
_
These sheets of rubber are .passed through mas
ticating mills consisting of two rollers rotating
,
A further vobject of my` invention lis to provide
a gasket made of gas expanded rubber.
Still another object of my invention is to pro
vide a novel combination. of gas expanded rub'
in opposite directions as inthe case of meshing '
gears. One roller, however, rotates slightly faster
than the other, so that the rubber fed’between so.
`20 ber which retains its flexibility and a hard rubber.
Vthe rolls tends torub on the surfaces of the'dif
There are other objects of myinventicn which
together with the _foregoing will appear in the
extended descriptionwhicli is to follow, in which:
Figure 1 is a perspective 'view illustrating one
25 >of many applications _of the gasket.
Figure 2 is a perspective view illustrating one
ferent speed rolls and a nib is formed as shown
form of my novel gasket.
'
Figure 3 is a perspective view illustrating a
13o
modiñed form of my novel gasket.
at IL'Fig. 2, of the copending application, S. N.
s'l1"1,55ll, referred to4 above. The extent of thisk
nib- depends on the relative speeds of the rolls 25"
and the nib in turn determines how much of the X
two surfaces l2 and. i3 of the rubber engage and
are masticated-_by the respective rolls I4 and I5;
The rolls are steam heated to a temperature ,
of approximately 150? F. as the rubber sheets are
fed between them. The rubber-‘is masticated or
`
Figure 4‘is- a perspective View illustrating a
modiiied form of mounting my novel gasket.
» sofœned in this process, the individual sheets
combining into a single mass of soft rubber, the
Figures .5 and 6 are perspective views of fur
‘l ther modiñed form of gaskets.
`
Figure '1 illustrates themounting of a plural
35 ity of gaskets.
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degree of mastication depending on the spacingv
of the rolls, the temperature and the period of 35
operation. We have found, however, that e. mas-_
The rubber composition which I use is an exl vtication of one pound per minute at a roller
temperature oi' 159° F. is sufficient for our pur
I lpanded rubber impregnated with a gas, prefer
` ably nitrogen, and expanded to more than eight poses.
'
To this resulting soft rubber mass is now add
4G times its original volume by a novel process' de
scribed in cao-pending application S. N. 717,550', ed an asphalt product or soft bitumin, such as
ñled March 27, 1934, of which I am a joint yap 7 suiîron or minerai 'Y rubber. This asphalt is di->
-,
plicant.
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vided into iine particles and passed through a_ six
, As, there described, a novel rubber composition teen mesh sieve. While the rubber revolves on the
(details of which will be given hereinafter) Ycom- . masticating rollers, these particles of bitumin are
45 prising a cellular rubber in which each of the
minute cells containing gas at a high pressure are
» sealed.
This sealed cellular rubber is relatively
much softer than solid rubber, thus supplying
0 one of the essential properties desired. inasmuch
as each cell is sealed from all other cells, it does
not absorb water or moisture from the air and
therefore is not so readily 41attacked `by atmos
pheric conditions. FinallyVit may be given Ycon
55 siderably greater ruggedness than can be obtained
shovelled on and are uniformly distributed over
the rubber.
The heat of the rubber melts the
bitumin' which penetrates into and is absorbed
by the rubber.
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’ The bitumin acts as a flux at low temperatures 50
in the stage ofv partial vulcanization to be ex
plained hereinafter. Anyother low temperature
flux may be substituted, i. e., a low melting hydro
carbon of the asphaltic group of a bituminous or
waxy nature havingiiuxing properties, such as 65
2
2,121,827
paraffin wax and stearic acid'. During this stage
the rubber has turned from a light to a dark color.
Ground gilsonite, divided into even finer par
ticles than bitumin and passed through a one
hundred and sixty mesh. sieve, is now sprinkled
or shovelled on the rubber, still passing through
the masticating rolls. Gilsonite isr an asphalt like
bitumin, but has a much higher melting' point.
It will, accordingly, not be meltedvby the rubber'
10 but will nevertheless penetrate into, impregnate
and be absorbed by the soft, spongy mass of rub
. ber. Gilsonite functions as av flux in a high tem
strips or slabs of about one-half inch in thick
ness and two feet'in length. The distorting ef
fect of passing the rubber through the rolls is now
again corrected by providing a second twenty
four hour rest period in a dark, warm„dry room
at about the same temperature as- the previous
rest period. Again," thelength of the rest period
may vary, but at least twenty-four hours is nec
essary and the longer this period, the more nearly
the rubber is restored to normal.
‘
10
The rubber is now placed _on a warmer millv
perature stage to be described hereinafter, and
may accordingly, be replaced by any suitable high
15 temperature flux suchas a high temperature
asphalt. In using the expression “flux”, it will
consisting of two rollers rotating at the same
speed. The rubber is fed between the rolls
maintained at a temperature offrom 120° to 140°
F., This is continued until the rubber again be
be understood that we mean a substance acting to
posite'mass and during which the rubber may be
'amalgamate or assist in the vulcanizing.
comes soft and forms into a uniform plastic com
formed into slabs, boards, etc., after which a fur
summarizing the above, three stages have been
20 described. In- the first, the rolls were heated to ther rest period of twelve hours is provided.' Or,
a temperature of 150° F. while masticating or 1 if desired, the rubber may be -passed through a 20
forcing machine which we preferto use for pre
forming the rubber in any desired shape, such as
wings, struts, pontoons, etc. If pre
ing twenty-four pounds of rubber, twenty-four aeroplane
the forcing operations may also be used
minutes may ordinarily be required for this oper ferred,
to soften the rubber in the earlier roller stages 25
described
hereinbefore.
In the second stage, a ?iw temperature flux is
f
’I‘he
various
stages of treatment described above
applied to the rubber as it continues to pass over
the rolls in the proportions given above and this, have resulted in agitating the rubbento such an
80 by reason of the heat, melts into and is absorbed extent that a quantity of air has been absorbed
by the rubber. The presence of this air may have `30
by the rubber.
_
» In the third stage, a high temperature ñux is Y serious deteriorating effect duiìing the subsequent l
stages to be described hereina ter. This may be
admixed with the rubber while it passes through described as follows: I
f
the rolls, again in the proportions given above.
Like glass, rubber is a> plastic or super-cooled
_als The second and thirdI stages take fourteen viscous liquid. Normally, it would be crystalline,
minutes additional to- the twenty-four minutes but is prevented'from becoming so because of the 35
` for mastication' and result in a vrubber impreg
complexity of the molecules which are large and
nated with a high‘and low temperature hydro
slow-moving due to the viscosity of the mixture.
carbon. The molecular structure of rubber is This
super-cooled viscous liquidis chemically an
.49 theoretically describedas normally being in the' unstable
product which -.tends to stabilize itself.
form of a spiral. `This may be thought as giv-t
Thisv is particularly true if the rubber is warmed
ing to the rubber its elasticity and strength. to
just below melting point which favors crystal- '
lDuring the working oi’ the ’rubber described above, lization.
The presence of air under these condi
a disturbance of the molecular structure appar ' tions is particularly conducive to crystallization,
ently occurs and the ru ber tends to lose its a simple oxidation resulting from a relatively sim
45
natural qualities.
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It is essential to provide "a, rest period for the. ple rubber compound which crystallizes out.
' Moreover, rubber oxidizes easily because it has
' rubber at this stage of the operations to permit
4unsaturations or double bonds which' tend to
the rubber to restore itself to its original condi
readily combine with the oxygen, lespecially under
the influence' of heat and pressure, thus making ,
Accordingly, in the next or fourth stage, the
the
rubber brittle. In the presence of air, rub
rubber, now flat, soft and porous, is permitted to
therefore, tends to oxidize. Attacked or oxi
cool oü, and is left to rest for about ~twelve hours, ber,
preferably in a dark, dry room at a temperature dized by even a small amount of air, the rubber
brittle, as is well known.
“
56 of from 80° to 100"` F. 'I'he longer the rest period, becomes
Tov
prevent
this,
the
rubber.
as
is
commonlythe more the rubber regains its original condi
vulcanized, i. e., stabilized. This con
tions, but we have found that twelve hours will ~known,.is
sists in heating the rubber with sulphur to .form
softening4 theQ rubber to combine the individual
‘ sheets into a single soft, spongy mass.
ation.
tion.
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Assum
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ordinarily be suilicient to restore it to about' itsl a vulcanized or stable product so that it no longer
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tends to combine with oxygen in the air. The
Following this rest period, these slabs of rub
sulphur forms a mixture of complex compounds,
ber are placed on rolls maintained at tempera
tures of from 120° to 130° F. As the rubber which prevents crystallization and oxidation.
` The presence, however, of even a small quantity
passes -between the rolls, additional slabs are add
of air may result in an oxidation for the reasons
original condition.
to
ed, 4which ultimately combine into a soft mass of
65 rubber.
When the mass has been formedwith
adjacent engaging surfaces adhering,1 sulphur
explained above, even before vulcanization sets in.
f Accordingly, it is important to force out all the I
and light calcined magnesia, in the proportions ' air that may have mixed with the rubber before
givenabove, are added as the rolls rotate. Sul
phur is the vulcanizer and the light calcined
magnesia is the rubber toughener. Any equiva
lent `rubber toughener, such as zinc oxide, may
replace thecalcined magnesia. For thorough ab
sorption, the rolling is continued'for a period of
about twenty minutes.
.
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the stageof partial vulcanization, to be described,
occurs.
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To this end, the 'rubber is passed between suc
cessive calenders maintained at a temperature of 70
from 130°. to 150° F. ‘The calender mill comprises
a series of rolls decreasingly spaced from each
other in 'successive steps. In the first step, as
--shown- in-Fig. 4, of the application S. N. 717,550
Theproduct is now removed from the ro _ in .referred to above, the rolls are relatively far
_ 3
» 2,121,827
under pressure in its individual cells. The rub
apart, in the next stage,‘clo'ser, etc. The ,rubber
ber sheets are now removed from the containers
passing through ' the calenders forces _all the
trapped air .out and is reduced in size. After
the rubber passes the last rolls, a sheet of cloth
with the result that the pressure is removed and
the gas inthe cells immediately expands the rub?
is applied thereto to close faults appearing in the
rubber and to prevent the rubber from contract
ber about four times.
,
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The partially cured rubber is now placed in a
ing. The cloth, having a limited expansion, keeps . mold suitably constructed to produce any of_ the
forms of rubber shown in Figures 2 to 7. These the stretch in rubber and maintains it a predeter
~
mined thickness.
,
may be triangular, trapezoidal, square, arched
~
or -*any other desired- shape.
The rubber is now cooled to room temperature
. 'and the cloth removed, leaving a sheet of un
. treated, rubber.
- The partially cured rubber placed -in molds for >
The product is now ready lfor „producing the special shapes of rubber desired
is new subjected to the final vulcanization. Each
znold is placed in a rnold ofthe desired dimen#A
15 ucts. Apprommately ten .such sheets of -rubber sions. 'Each mold is placed between platens and 15
saturated steam is applied at ninety-five pounds
» may be placed with metalsheets interposed be
tween each sheet of rubber, and the whole placed I for about forty to forty-five minutes. This is the
final stage of the process of the curing and ex
in a metal container having an internal dimen
sion slightly larger than the combined sheets. A pansion. The rubber expands to the size of the
cover is then fastened into place on the con» molds and at the same time complete curing or 20
tainer. A number of these containers are then vulcanization of the rubber is obtained. The
placed into va gassing autoclave which is then, steam is now turned off and the product per
closed and fastened'down. Thev autoclave has mitted to cool. If desired, cooling may be has
previously been >aired by passing steam through tened by applying cold water. The end product
the container andheating it to a temperature of is an expanded cellular inert gas filled product
weighing about five pounds per cubic foot. `
from 180° to212° F. to reniove moisture.
the two -‘ldnal -stages‘of vulcanization to be 'de
- scribed. These vary somewhat for different prod
This stage, duringfwhich the vulcanization is'
A vacuum pump is then connected to an inlet
of the container to extract the air until a vac
uum of about five inches is obtained. The evac
completed, >must take place within forty-eight
hours after the completion of the partial :expan-->
sion and vulcanization. Otherwisesumcient gas
lso uation is important- for. the reasons already
pointed >out hereinbefore. When the container
may. escape from the partially vulcanized rubber
has been evacuated, gas is admitted into the
autoclave at a pressure of from 150 m200 atmos
so, that there is a material loss in volume._
pheres. Any inert gas, preferably non-combusti
ble, and having no affinity for raw rubber, such
as nitrogen (N), ammonia (NH3), helium (He),
f 'may be used for this. Thus air. would be disas
trous, if used. Forcing air into raw rubber at
'several hundred atmospheres pressure and at or
into the new dough in small percentages. `
It is also possible, alternatively,Í in the event
that `more than forty-eight hours is to elapse,
to take care of this condition by carrying on the
first stage to >a further degree of vulcanization
near vulcanizing temperatures, would tend to
oxldize the rubber very rapidly and'before vul
than originally Vcontemplated by applying the
>steam for a longer period of time or at a Ahigher
` canization set in, resulting in an undesirable
temperature than is obtained by eight pounds of
product. _Moreover, it would be dangerous> prac
tice, because a spark would cause a terrimc explo-`
sion.
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In the event that more than i’orty-eighthours
Aelapse before the' last stage of the process-occurs..
it is preferable to regi-ind the material and add'it as f
In fact. I have found from experiments that 46
.
the first stage can be carried on at from> eight to
While the gas is being forced linto the rubber,
steam at eight pounds pressure is admitted to
sixteen pounds of steam, although better results
are obtained at the 1ower"range..„When the
the steam chest. , About thirty minutes- are nec
greater degree of vulcanlzation occurs, the mate
rial can be kept for a longer period than forty 50
eight hours without the gas diffusion.
The ñnal product; Vdepending upon the per
The conditions in this stage are critical and centages of the various ingredients used, is‘ a
accordingly both the pressure of the gas and the soft, light rubber of multitudinous minutesealed
temperature of the container must be correct.v cells, each ceil apparently containing gas at a 55.
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The rubber, while exposed to the» gas, is in a soft high pressure.
The resulting rubber units may be secured ‘to
plastic state and therefore readily receives the
gas. The. eight pounds of steam in the steam eachother in any well known manner as by
jacket produce a temperature at whichpartial vulcanizing and in the relative arrangements
vulcaniaation proceeds to a substantially uniform' shown. The larger arches of the upper layers 60
degree lthroughout the body of the rubber. This will provide increased softness, the smaller
partial vulcanization functions to harden the arches of the lower layers will provide shock
_
rubber suñiciently so that it retains the gas absorbing action. '
In order to produce further differentials in the
forced into ‘the rubber. At this time substan
tially little or no -,expansion of the rubber -has , effect of softness and hardness, a layer of sponge 85
taken place due to its confinement within the rubber may be vulcanized to a layer of cellular
essai-y for the container to reach a stable teni
perature and thereafter the container is main
tained at the same temperature continuing to
supply steam at about' eight pounds pressure.
rubber.
container.
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under atmospheric conditions and subsequently
In Figures 2 to 4, I have illustrated the finally
molded rubber il, trapezoidal in- shape. The
f Excess gas in_the autoclave is now removed.
The rubber being partially cured, will _hold gas
vulcanized to the fabric as illustrated in Figure ’7.
In Figure 5, I_have shown a modified-shape ofA 75
The` autoclave is' now permitted to cool oif
70 cold water is forced through the steam jacket ` rubber iiA is secured as by vulcanizaticn to a 76
until a temperature of 60°-70° F. is reached. fabric strip i2 either at the end of the fabric
This permits the rubber now in semi-cured state v as in Figure 2 or intermediate thereof as in Fig
ure 4. If desired, a plurality of gaskets may be
to set.
9,121,827
gasket l. e., in which the rubber has been molded
into a square shape as illustrated at i5.
In Figure 6, Ii? have shown the rubber gasket
molded in the form. of an are iB. These are i1
lustrations of only some of the numerous shapes
into which the gasket can be molded. `
'
In Figure 3, I have illustrated the rubber gas
ket il vulcanized to a. hard rubber strip I7.
cabinets, and other purposes where a seal is
needed between two objects. It is of especial
utility as windlass cord, such as is employed
around the windows in automobiles. Accord-
-
ingly, I do not -wish to be limited by the specific _*
illustrations of my invention, but only by- the
appended claims.
I claim:
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It will be understood that I may use a rubber
,1; A gasket, adapted for exposure to delete
10 base or any other suitable composition instead
rious weathering influences, comprising a fabric
of the fabric i2 as a support for the gasket. strip and closed cell gas expanded rubber se
Moreover, I may use sponge rubber formed in any . cured thereon, said closed cell gas expanded rub
other well known manner besides that. given in ber containing a multiplicity of small sealed cells
detail above by way of illustration..
of inert gas throughout uits mass.
.
15 ,In Figure 1 I have illustrated one construc
2. A gasket, adapted for> exposure t9 delete
tion ix‘iwhich my'gasket may be employed. As rious weathering influences,` comprising a fabric 16
shown in this figure, supported between frames strip and closed cell gas expanded rubber se
2| and 22 is a door 23 hinged at 24 and having ¢cured- thereon, said closed cell gas expanded rub-`
a panel 25. The rubber gasket Ii, of the form Vber containing a multiplicity of small sealed
20 shown in any one of the ~other figures, is secured cells of inert gas throughout its mass, said
through the fabric l2 to the door. A molding or closed cell gas expanded rubber being so posi,
door-stop 26 is engaged by the rubber gasket il tioned as to be directly exposed-to said dele
when the door is closed in the position shown, terious weathering influences.
by means of which a seal is vformed which has
3. A gasket, adapted for exposure to delete
substantially no set andy will' not, therefore, re- t rious weathering influences, ~comprising a fabric.
sult in any leaks after a relatively short period
0f use'.
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Although in the above illustration I have
shown a rubber’ gasket applied to doors, but it
30 will >be obvious that it may also be applied to
the sealing of trucks, refrigerator doors, window
sills-where it may be used as weatherstripping
shlpping'containers, storage boxes and storage
strip;` closed cell gas expanded- rubber secured
thereon, said closed cell gas expanded rubber
containing ka multiplicity of small sealed cells
of inert gas throughout its mass; and a layer
of rubber laminated'over said closed cell gas ‘30
expanded rubber to provide a strong, long wear
ing buiïer surface for said gasket.
.
r
DUDLEY ROBERTS.
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