4296 4300.output

* GB784703 (A)
Description: GB784703 (A) ? 1957-10-16
Improvements in or relating to the manufacture of gloves from rubber or
flexible thermoplastic materials
Description of GB784703 (A)
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**WARNING** start of DESC field may overlap end of CLMS **.
COMPLETE SPECIFICATION
Improvements in or relating to the Manufacture of Glovesl from
Rubber or Flexible Thermoplastic Materials
We, LONDON RUBBER COMPANY LIMITED a British Company, of Hall Lane,
Chingford,
London, E.4, do hereby declare the invention, for which we pray that a
patent may be granted to us, and the method by which it is to be
performed, to be particularly described in and by the following
statement:
This invention relates to the manufacture of gloves from rubber or
flexible thermoplastic material by dipping into a dispersion of the
rubber or other material a former of the desired shape and size so
that a film of the material is deposited on the former, and sub
sequently heating the former with the film thereon.
Gloves manufactured in this manner have a better surface internally
than externally, and it is therefore customary to turn the finished
gloves inside out before sale and use, so as to provide an improved
appearance. Moreover, it may be advantageous to have a roughened
external surface on at least some parts of a glove, and this can be
obtained, if the glove is turned inside out after being manufactured,

by suitably roughening the former.
It has been found, however, that a glove, when turned inside out, is
considerably distorted so that it does not lie closely on the hand,
and has an unnatural appearance. The object of the present invention
is to avoid this disadvantage.
The present invention comprises a method of manufacturing a glove of
rubber or other flexible thermoplastic material which consists in
preparing a former having the shape of a glove which has been produced
on another former simulating the true shape of a hand and has been
turned inside out, forming a glove thereon by dipping in the known
manner, and turning the glove so formed inside out
The former may be prepared by any one of those methods described in
our Patent Application No. 34219/54 (Serial No. 784,702) in which the
former is produced in a mould having the shape of an inside-out glove
or by any other method such as, for example, by turning inside out a
glove made on a former simulating the true shape of a hand, filling
the said glove with any suitable material to give it a degree of
rigidity, and copying its shape by means of a copying machine.
The former is dipped in the usual manner into a dispersion of the
material from which the gloves are to be formed so as to receive a
film of that material, and the film is subjected to heat treatment in
the known manner.
After being stripped from the former the glove is turned inside out,
and then has substantially the shape of a glove made on a former
simulating the true shape of a hand, its external surface being that
which was in contact with the former,
What we claim is: -
1. The method of manufacturing a glove of rubber or other
thermoplastic material which consists in preparing a former having the
shape of a glove which has been produced on another former simulating
the true shape of a hand and has been turned inside out forming a
glove thereon by dipping in the known manner, and turning the glove so
formed inside out.
2. The method of manufacturing a rubber glove substantially as herein
described.
PROVISIONAL SPECIFICATION
Improvements in or relating to the Manufacture of Gloves from
Rubber or Flexible Thermoplastic Materials
We, LONDON RUBBER COMPANY LIMITED, a British Company, of Hall Lane,
Chingford,
London, E.4, do hereby declare this invention to be described in the
following statement:
This invention relates to the manufacture of gloves from rubber or
flexible thermoplastic material by dipping into a dispersion of the

rubber o; other material a former of the desired shape and size so
that a film of the material is deposited on the former, and sub
sequently heating the former with the film thereon.
Gloves manufactured in this manner have a better surface internally
than externally, and it is therefore customary to turn the finished
gloves inside out before sale and use, so as to provide an improved
appearance. Moreover, it may be advantageous to have a roughened
external surface on at least some parts of a glove, and this can be
obtained, if the glove is turned inside out after being manufactured,
by suitably roughening the former.
It has been found, however, that a glove, when turned inside out, is
considerably distorted so that it does not lie closely on the hand,
and has an unnatural appearance. The object of the present invention
is to avoid this disadvantage.
The present invention comprises a method of manufacturing a rubber
glove which consists in preparing a former having the shape of a glove
produced on another former simulating the true shape of a hand and
turned inside out, and turning the glove inside out after manufacture.
The former may be prepared by any of the methods described in our
Patent Application
No. 34219/54 (Serial No. 784,702) or by any other method such as, for
example by turning inside out a glove made on a former simulating the
true shape of a hand, filling the said glove with any suitable
material to give it a degree of rigidity, and copying its shape by any
suitable method.
The former is then dipped in the usual manner into a dispersion of the
material from which the gloves are to be formed so as to receive a
film of that material, and the film is subjected to heat treatment in
the known manner After being stripped from the former the glove is
turned inside out, and then has substantially the shape of a glove
made on a former simulating the true shape of a hand, its external
surface being that which was in contact with the former.
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* GB784704 (A)

Description: GB784704 (A) ? 1957-10-16
Articles comprising boron nitride and refractory oxide and the manufacture
thereof
PATENT SPECIFICATION
784704 r Date of Application and filing Complete Specification:June
21, 1955.
No 17885/55.
Application made in United States of America on Oct 25, 1954.
Complete Specification Published: Oct 16, 1957.
Index at acceptance:-Class 22, J( 1: 6: 7: 9: 12: 19: 20: 22).
International Classification:-C 04 b.
Articles Comprising Boron Nitride and Refractory Oxide and the
manufacture thereof We, THE CARBORUNDUM COMPANY, of Niagara Falls, in
the County of Niagara and State of New York, United States of America,
a Corporation organized and existing under the laws of the State of
Delaware, United States of America, do hereby declare the invention,
for which we pray that a patent may be granted to us, and the method
by which it is to be performed, to be particularly described in and by
the following statement: This invention relates to shaped bodies or
articles of manufacture consisting essentially of refractory oxide and
boron nitride, and to compositions and methods for making the same.
There is a constant search for new compositions or bodies that possess
unexpected combinations of properties essential to or desirable in
specific fields of use The bodies of the present invention possess
certain combinations of properties and characteristics that render
them of considerable value, and they offer outstanding possibilities
in a number of fields of use It is, therefore, to be understood that

the refractory oxide-boron nitride bodies hereinafter more fully
described are not to be considered as restricted to any particular
field of use However, their outstanding characteristics as refractory
mater Ials are particularly worthy of note and make them especially
suitable for many refractory purposes The present invention therefore
will be described primarily in resnect of the use of the herein
described products for refractory purposes, although not intended to
be limited thereto.
Above all a refractory body must possess refractoriness, that is an
ability to stand up under exposure to high temperatures without undue
chemical or physical change Other desirable characteristics sought in
a refractory body or shape include an ability toi resist sudden
changes in temperature without cracking or otherwise breaking down, a
satisfactorily high mechanical strength at elevated temperatures as
well as at room temperature, l'p chemical inertness and resistance to
various corrosive and erosive substances and conditions, a resistance
to oxidation, and a density and hardness dependent upon the use to
which the refractory body or shape is to be put.
In order to obtain a high degree of perfection in one or more of the
above properties, it has usually been necessary to forego the benefits
of maximum performance in respect to certain other desirable
properties Consequently, various refractory compositions exceptionally
suitable for one use frequently are entirely unsatisfactory for other
purposes.
There is, therefore, a continual demand for refractory bodies of new
compositions that will meet those demands of a special nature which
require novel combinations of properties not to be found in
compositions already available.
It is an object of the present invention to provide bonded refractory
bodies or shapes of unusual and distinctive compositions and
properties.
It is another object to provide refractory bodies or shapes having a
particular combination of properties heretofore unavailable in
refractory compositions.
It is a further object to provide practical methods and compositions
for making such articles.
The shapes or bodies of the present invention comprise boron nitride
and refractory oxidic material The amount of boron nitride present in
the bodies may range from almost zero per cent, such as 1 or 2 per
cent, to almost 100 per cent by weight of the bodies.
The preferred compositions of the present invention, however, contain
only un to 30 per cent by weight boron nitride The bodies of the
present invention are hard and dense.
having a density of 85 per cent or more of the theoretical density.

The boron nitride used in carrying out the present invention may be
either a high or a low purity boron nitride material available on the
market For example, it may be a low purity boron nitride material made
in accordance with the process described in Specification No 13838/53
(Serial No 742,326) This boron nitride material is made by nitriding a
porous pelleted mixture of boric acid or boric oxide and tricalcium
phosphate by heating it in ammonia gas at a temperature of around 900
C After nitriding, the resultant nitrided pellets are treated with
dilute hydrochloric acid to dissolve the tricalcium phosphate and
other extraneous materials The undissolved boron nitride after washing
with water is usually treated with hot 95 % alcohol solution to
further lower the content of extraneous material The material is then
dried by allowing to stand overnight at room temperature followed by
heating for 2 hours at 300 F A typical analysis of the boron nitride
is as follows:
Boron 41 45 % Nitrogen 45 60 % Free Boric Acid (Calculated as HBO 0,)
75 % Silica 28 %o, Calcium trace Phosphate (P 04) trace Material
volatile at 110 C 26 % Although this material contains no
alcoholsoluble material, it is believed that it contains up to about
20 % of an oxidic boron compound tied up either chemically or
physically so as to be alcohol-insoluble.
An example of a high purity boron nitride material that may be used in
the process of the present invention is the mtserlal made in
accordance with the process described in specification No 6158/55
(Serial No.
777,000) Boron nitride material is made in accordance with this patent
application by first preparing a low purity boron nitride material,
such as the boron nitride material prepared in accordance with the
process of specification No 13838/53 (Serial No.
742,326) and then heating the low purity boron nitride material in an
atmosphere of ammonia at a temperature ranging from 1100 to 1500 C A
typical analysis of the resultinc high purity boron nitride material
is as follows:
Boron 43 3 % Nitrogen 53 3 % Oxygen 2 23 % Silica 25 % Calcium Nil
Iron and aluminium oxides 16 % The refractory oxidic material employed
in the process of the present invention may be any of the well-known
simple refractory oxides, preferably being selected from the groun
consisting of zirconia, alumina, thoria, beryllia and combinations
thereof Instead of employing one or more simple refractory| oxides,
complex refractory oxidic material mayg be used, such as the various
refractory silicates or aluminates, including mullite, sillimanite,
olivine, and refractory porcelains When 65 zirconia is employed, it is
preferably a stabilized zirconium oxide in which all or a major
portion of the zirconia is of the cubic crystalline variety such as a

zirconium oxide that has been stabilized with around 5 % of calcium 70
oxide.
In accordance with the present invention, shaped articles of
manufacture comprising boron nitride and refractory oxidic material
are made by the method which comprises pre 75 paring or selecting a
raw mix comprising finely-divided refractory oxidic material and boron
nitride, and consolidating the raw mix by the simultaneous application
of pressure and heat, that is, by hot pressing 80 The hot pressing is
carried on by heating the mold containing the raw mix in an inert
atmosphere within the temperature range of 1400 C to 1900 C,
preferably from 1600 C.
to 1700 C The maximum temperature of 85 1900 C should not be exceeded
in firing, because firing at higher temperatures frequently causes
partial disintegration, part of the refractory oxide being converted
to a boride.
For example, when a body consisting of 80 % 90 stabilised zirconia and
20 % boron nitride was fired at 2000 C it Dartially disinterated the
presence of zirconium boride having been established by X-ray
diffract;_n analysis.
The articles of the present invention are 95 hard and extremely dense
and have a low sandblast penetrati-n factor The densities of the hot
pressed bodies are greater than 85 % of the theoretical density,
frequently being as high as 95 % or more of the theoretical density
100 It is therefore apparent that by practising the process of the
present invention bodies of extremtnely low porosity can be produced.
Furthermore if the raw mix employed consists essentially of high
purity boron nitride material 105 and refractory oxidic material, hard
dense bodies composed of, or consisting essentially of, boron nitride
and refractory oxidic material can be made.
In contrast to the high density, hard bodies 110 of the present
invention made by hot oressing, bodies of similar composition
consolidated by cold pressing and sintering are in most instances
relatively weak and porous, even when low percentages of boron nitride
are employed 115 Boron nitride-refractory oxide bodies consolidated by
cold pressing and sintering and containing more than 2 ( O % by weight
boron nitride, usuallyv are so weak that they are easilv crumbled by
hand Therefore, boron nitride 120 refractory oxide bodies made by cold
Dressing and sintering are hiurhlv unsatisfactory for uses where
bodies of high strength, hardness, density and purity, and/or
containing high percentages of boron nitride are required 125 To
demonstrate the practice of the present invention, the following
examples are given:
784,704 784,704 EXAMPLE 1.
In accordance with the practice of the present invention, boron

nitride-refractory oxide bodies in the form of cylinders 1 " diameter
x about 1 " long were made as follows:Intimately conmmingled granular
raw mixes having a particle size of 20 microns and finer and
consisting of refractory oxide and high purity boron nitride material
made in accordance with the aforementioned Patent Application No
6158/55 (Serial No 777,000) were prepared by passing the mixed
ingredients through a fine meshed screen several times.
The desired amount of each, raw mix was then put in a mold and the
mold and contents were heated under a pressure of about 2000 pounds
per sq in at the temperature indicated in Table I below, the mold and
contents being held under pressure a maximum temperature until the
required density has been obtained Table I below presents fabricating
data and physical properties of the various bodies consisting
essentially of boron nitride and refractory oxide made in accordance
with the process of the present invention.
TABLE I
Bodies Consisting of Boron Nitride and Refractory Oxide Fired in an
Atmosphere of Helium Raw Mix Firing Sand Apparent Theoretical Percent
Bar Composition, Type BN blast Density Density Theoretical No % by
weight Used Max Temp Penetration gms /cc gms /cc Density 1 80 % Zr O
2; % BN Pure 1650 C 006 " 4 19 4 38 96 % 2 80 % A 1203; % BN Pure 1600
C 023 " 3 15 3 41 92 % 3 80 % Mullite; % BN Pure 1600 C 015 " 2 75 2
82 98 % 4 80 % Th O 2; % BN Pure 1800 C 032 " 5 35 5 86 91 % 50 % Zr O
2; % BN Pure 1700 C 010 2 85 3 22 88 % 6 10 % Zr O 2; % BN Impure 1800
C 004 " 2 14 2 40 89 % 7 12 % Th O 2; 88 % BN Impure 1800 C 006 " 2 25
2 49 90 % Standard penetration on plate glass when subjected to the
same penetration test is 010 ".
As can be seen by the data in Table I, superior, hard, high density
bodies having a wide range of compositions can be made by the
preferred hot pressing process of the present invention.
EXAMPLE 2.
To demonstrate the inferiority of the physical properties of cold
pressed and sintered boron nitride-refractory oxide bodies in contrast
to the outstanding physical properties given in Table I above for
similar compositions hot pressed in accordance with the present
invention, a series of pieces in the form of small test bars 1 2 " x ,
x 4 r" were made as follows:
Intimately commingled mixtures of refractory oxidic material and boron
nitride of the aforementioned high purity variety, were prepared The
mixes had a particle size of 20 microns and finer To about 10 parts by
weight of each mixture was added 5 by weight of "Carbowax" No 4000
dissolved in 1 part by weight of benzene, and the thusly formed raw
mixes were ground in a mortar until the benzene had evaporated
"Carbowax" No.

4000 is a trade mark denoting a polyethylene glycol composition The
mixtures were then molded to the desired shape at pressures up to
'30,000 psi The temporary binder of "Carbowax" was removed by slowly
heating the molded shapes at 400 C The pressed shapes were then heated
in an atmosphere of helium Table II below presents fabricating data
and physical properties of the various bodies comprising boron nitride
and refractory oxide in various proportions made by cold pressing and
sintering.
784,704 TABLE II
Bodies Consisting of Boron Nitride and Refractory Oxide Fired in an
Atmosphere of Helium Firing Raw Mix Type Sand Apparent Theoretical
Percent Bar Composition BN Max H Iolding blast Density Density
Theoretical No % by weight Used Temp Time Penetration gms/cc gms/cc
Density 8 80 % Zr O 2; Pure 1650 C 60 Not co% BN Min herent 9 80 % A 1
03; Pure 1650 C 60 Not co% BN Min herent 80 % Mullite; Pure 1650 C 60
435 " % BN Min.
11 80 % Th O 2; Pure 1650 C 60 Not co% BN Min herent 12 80 % Zr O 2;
Pure 1800 C 60 310 " 2 80 4 38 64 % % BN Min.
13 80 % A 1203; Pure 1800 C 60 Soft 1 73 3 41 51 % % BN Min.
14 80 % Mullite; Pure 1800 C 60 375 " 1 88 2 82 67 % % BN Min.
80 % Th O 2; Pure 1800 C 60 Soft 3 15 5 86 54 % % BN Min.
Standard penetration on plate glass when subjected to the same
penetration test is 010 ".
Too soft to test.
It is to be noted that the compositions of bars 8 through 15 are
identical with the compositions of bars 1 through 4 in Table I Cold
pressing and sintering these compositions, even at temperatures as
high as 1800 C with holding times of 60 minutes, resulted in bodies
having densities ranging only from 51 to 67 per cent of the
theoretical densities for non-porous bodies of the same compositions.
In contrast densities approaching 100 per cent of the theoretical
densities for completely non-porous bodies are obtained by hot
pressing raw mixes containing any desired percentage of boron nitride.
While in the above examples the practice of the present invention is
demonstrated primarily by raw mixes containing only a single simple
oxide, as was pointed out above more than one refractory oxidic
material can be included in the raw mixes of the present invention
Furthermore, if desired, minor amounts of an inert refractory filler,
such as a refractory boride or silicide, can be included in the raw
mixes in place of some of the refractory oxidic material to produce
bodies that are satfsfactcly for cer-tin uses.
While the above examples have described the making of molded bodies in
which the body is consolidated to the exact shape or form in which it
is intended for use, the present invention is not intended to be so

restricted Another way of making and using the refractory oxide-boron
nitride bodies of the present invention is to consolidate the raw
batch into briquettes or other shapes, after which the resulting
briquettes or shapes are crushed to granular form of the desired grit
size The resulting granular material can then be used in loose
granular form as high temperature refractory material, as layers of
insulation in industrial furnace chambers, as insulation around jet
engines and rocket combustion chambers, and the like It may also be
used as loose filtering media or as catalyst or catalyst carrier
materials The granular material can also be bonded by means of
sintered metals, vitreous or ceramic bonds, or other bonding material,
or it may be cold pressed and sintered or hot pressed per se to form
articles suitable for many of the industrial uses set forth elsewhere
herein.
It is to be understood that the products of the present invention in
their various modifications are not limited to any specific field or
fields of use such as might be defined by the specific examples
previously set forth.
The products can be made in any desired shape as well as provided in
granular aggregate form They are, therefore, not only suited for many
of the uses for which industrial refracteries are required, including
bricks, blecks, setter tile, muffles, kiln furniture, and special
shapes for application in and around furnaces and other high
temperature equip% boron nitride and at least 70 % refractory oxidic
material.
3 As a new article of manufacture, a body as claimed in claim 1 or 2,
in which the refractory oxidic material consists of zirconia, alumina,
thoria, beryllia, or mixtures thereof.
4 As a new article of manufacture, a body as claimed in claim 1, 2 or
3 and containing an inert refractory filler.
A method of making shaped articles of manufacture comprising selecting
a raw mix comprising boron nitride and refractory oxidic material and
consolidating said raw mix to the desired shape by simultaneously
pressing and heating in an inert atmosphere at 14001900 C.
6 A method of makling shaped articles of manufacture as claimed in
claim 5, in which the refractory oxidic material consists of zirconia,
alumina, thoria, beryllia or mixtures thereof.
7 A method of making shaped articles of manufacture as claimed in
claim 5, or 6, in which the raw mix contains up, to 30 % boron
nitride.
8 A method of making shaped articles of manufacture as claimed in
claim 5, 6 or 7 in which the hot pressing is effected at 16001700 C.
9 A method of making shaped articles of manufacture, as claimed in any
of claims 5-8, in which the raw mix is placed in a mold and the mold

and contents are heated under pressure at 1600-1900 'C.
A method of making shaped articles of manufacture as claimed in any of
claims 5-9, in which the raw mix comprises refractory oxidic material,
inert filler and up to 30 % boron nitride.
MARKS & CLERK.
ment, but they are also well suited for many specialty
high-temperature applications, such as jet engine combustion chambers,
linings for exhaust nozzles, rocket combustion chambers and exhaust
nozzles, turbine blades, stator blades, lens fusion blocks, spark plug
bodies, and the like They are also suitable for the fabrication of
laboratory ware, including combustion boats, crucibles, burner holders
and other shapes The resistance of such bodies to chemical attack make
them highly suitable for the making of articles used in the
containing, conveying and handling of many acids, molten metals and
other corrosive chemicals, including such articles as chambers and
chamber linings, crucibles, pipes and pipe fittings, and other sundry
shapes The bodies of the present invention are also highly useful as
diffusion and filtering media, such as diffusion tubes and plates,
filtering tubes, plates and shapes, or as catalysts or catalyst
carriers and supports The materials and articles of the present
invention can also be used for making abrasive articles such as
grinding wheels, sharpening stones, razor hones, and other grinding
and polishing shapes and materials.
The present bodies offer possible applications in the electrical and
radio industry including supports in electric light bulbs, radio
tubes, X-ray tubes and radar equipment, resistors and grid leaks.
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* GB784705 (A)
Description: GB784705 (A) ? 1957-10-16
Refractory bodies containing boron nitride and a boride, and the manufacture

thereof
7 fi Date of Application and filing Complete Specification: July 22,
1955.
No 21245/55.
Application made in United States of America on Oct 25, 1954.
(Patent of Addition to No 742,327, dated May 18, 1953).
Index at acceptance:-Classes 22, J( 1: 2: 6: 7: 11: 12: 19: 21: 33);
and 70, F 2 A( 2: 3).
International Classification:-CO 4 bo COMPLETE SPECIFICATION
Refractory Bodies Containing Boron Nitride and a Boride, and the
Manufacture thereof We, THE CARBORUNDUM COMPANY, of Niagara Falls, in
the County of Niagara and State of New York, United States of America,
a Corporation organized and existing under the laws of the State of
Delaware, United, States of America, do hereby declare the invention,
for which we pray that a patent may be granted to us, and the method
by which it is to be performed, to be particularly described in and by
the following statement:-
This invention relates to improvements in or modifications of the
shaped bodies or articles of manufacture and the compositions and
methods for making the same, according to specification No 13839/53,
(Serial No.
742,327).
According to specification No 13839/53, (Serial No 742,327) bodies
stuch as refractory bodies comprise boron nitride and either zirconium
boride or carbon boride Such bodies are made by forming a mixture of
boron nitride and the selected boride, placing the mixture in a mold
and hot pressing said mixture at a temperature of at least 1800 C and
a minimum pressure of 500-750 pounds per square inch.
It is an, object of the present invention to provide alternative
materials for use in the manufacture of such bodies.

The shapes or bodies of the present invention consist of boron nitride
and either refractory boride material other than zirconium boride and
carbon boride, or zirconium or carbon boride together with the other
refractory boride The amount of boron nitride present in the bodies
may range from almost 0 %, such as 1 or 2 %, to almost 100 % by weight
of the bodies The preferred compositions of the present invention,
however, contain only up to 50 % by weight boron nitride, with the
best bodies containing not over 20 % by weight boron nitride.
The bodies or articles of the present invention are made by
hot-pressing the raw mixes in a graphite mold at a temperature
somewhat lPrice lower than the temperature at which the particular raw
mix becomes so plastic as to be extruded from the mold around the
plunger.
With compositions high in boride content, the maximum hot-pressing
temperature is usually slightly below the melting temperature of the
boride However where compositions high in boron are employed,
temperatures above the melting temperature in the neighborhood of 2500
C may be used The hot-pressing is preferably carried on at pressures
of from 500 to 750 pounds per square inch or more.
The boron nitride used in carrying out the present invention may be
either a high or low purity boron nitride material available on the
market For example, it may be an impure boron nitride made in
accordance with the process described in specification No.
13838/53, (Serial No 742,326) This boron nitride material is made by
nitriding a porous pelleted mixture of boric acid or boric oxide and
tricalcium phosphate by heating it in ammonia gas at a temperature of
around 900 C After nitriding, the resulting nitrided pellets are
treated with dilute hydrochloric acid to dissolve the tricalcium
phosphate and other extraneous tuaterials The undissolved boron
nitride, after washing with water, is usually treated with hot 95 %
alcohol solution to further lower the content of extraneous materials
The material is then dried by allowing it to stand overnight at room
temperature followed by heating for two hours at 300 F.
A typical analysis of the boron nitride is as follows:
Boron 41 451 % Nitrogen 45 60 % Free Boric Acid (calculated as H 3 BO
3) 75 % Silica 28 % Calcium trace Phosphate (P 04) trace Material
volatile at 110 a C 26 % Although this material contains no alcohol
ijc 4,705 soluble material, it is believed that it contai up to about
20 % of an oxidic boron cot pound combined either chemically
physically so as to be insoluble in alcohol ai water.
An example of a high purity boron nitric material that may be used in
the process the present invention is the material made accordance with
the process described specification No 6158/55, (Serial N
777,000) Boron nitride material is made accordance with this patent

application by fir preparing a low purity boron nitride materi such as
the boron nitride material prepare in accordance with the process of
specificathi No 13838/53, (Serial No 742,326), and the heating the low
purity boron nitride materi in an atmosphere of ammonia at a temper
ture ranging from 1100 to 1500 C We prefi a minimum temperature of
14000 C A typic analysis of the resulting high-purity borc nitride
material is as follows:
Boron Nitrogen Oxygen Silica Calcium Iron and aluminium oxides 43.3 %
53.3 % 2.23 % 0.25 %? nil 0.16 % We have further found that if boron
nitrid prepared in accordance with specification N,
13838/53, (Serial No 742,326), is sue sequently, before use, subjected
to a heatin pre-treatment in which the material is heate in an inert
atmosphere at a temperature in th neighborhood of 1900 to 2200 TC,
molde shapes containing the thusly treated materik are superior for
certain uses.
The refractory boride material employed i the process of the present
invention may b any of the well-known refractory borides othe than
zirconium boride and carbon boride, suca as titanium boride,
molybdenum boride chromiunm boride and mixtures thereof ins including
mixtures with zirconium or carbon a boride.
or The refractory borides used in carrying out ad the present
invention may be any 1 igh purity grade of refractory boride available
on the ide market It is preferred to use a product made of by reacting
a mixture of metal oxide, boron in carbide and carbon and/or metal to
produce in metal boride.
To In order that the invention may be more in clearly understood, the
following example is rst submitted as illustrative of compositions for
al, and the manner of carrying our the present ed invention.
on Raw mixes consisting essentially of boron en nitride (made as
described in specification No.
al 6158/55, (Serial No 777,000)) and finely a divided molybdenum,
chromium and titanium er borides were mixed by grinding together for
al 24 hours in alcohol in a ball mill lined with an sintered tungsten
carbide The resulting mixtures were placed in a cylindrical graphite
mold having two movable graphite plungers.
The assembled mold was placed in a graphite chamber of a high
frequency furnace and heated as follows: The temperature of the mold
was raised to preferably, a minimum temperature of 1600 C, e g 1600 TC
for the bodies incorporating molybdenum and chromium borides, and
approximately 1800 C le for bodies containing titanium boride, over o
a period of 1 hours and held at the stated temperature for 10 minutes
under a minirnum g pressure of 2000 p s i The furnace was then d
allowed to cool to room temperature The e furnace chamber was
cylindrical, 12 " long and d 4 " inside diameter and was closed during

the al heating and cooling periods except for an, opening in the topn
about one half inch in n diameter through which temperature observae
tions were made The table below presents r fabricating data and
physical properties of the h various bodies made in accordance with
this e, example of the process of the present invenf, tion.
BODIES CONSISTING ESSENTIALLY OF BORONNITRIDE AND METAL BORIDE Bar
No.
Raw Mix Composition Percentage by Weight Pretreatment of BN
SandMolding Molding blast Temp Pressure Penetration Apparent Density
gms/cc.
1 15 % BN; Prefired in 1600 C 2000 psi 006 " 5 75 % Mo 2 B No at 1900
C.
2 15 % BN; Prefired in 1600 C 2000 psi 009 " 4 15 % Cr 2 B N 2 at 1900
C.
3 80 % BN; None 1800 C 2000 psi 008 " 2 24 % Ti B 2 Standard
penetration on plate glass when subjected to the same penetration test
is 010 ".
784,705 784,705 While we have described in the above example the
making of various molded bodies in which the body is molded and fired
to the exact shape and form in which it is intended for use, the
present invention is not intended to be so restricted Another way of
making and using the nitride-boride bodies of the present invention is
to mold the raw batch of material into briquettes or other shapes or
otherwise compress a mass of the material having a composition in the
desired proportions, after which the resulting briquettes or
compressed bodies are hot pressed in a manner already described After
removal from the furnace, they are crushed to granular form of the
desired grit size The resulting granular material can then be used in
loose granular form as a high temperature refractory material or as a
layer of high temperature insulation material, as, for example,
insulation or protection around jet engines and rdcket combustion
chambers, or as a layer of insulation around industrial furnace
chambers It may, also be used as a loose filtering media or as a
catalyst or catalyst carrier material The granular material can also
be bonded by means of sintered metals, vitreous or Iceramic bonds' or
other bonding material to form articles suitable for many of the
industrial uses set forth elsewhere herein.
Likewise, articles or bodies can be made in accordance with the
present invention in which pore-forming materials are incorporated in
the raw batch from which the body is made for the purpose of providing
a greater degree of porosity in the final body A pore-forming material
such as carbon, which requires oxidation for removal from a body would
require a preliminary burning out of the pore-forming material at
lower temperatures Therefore, the pore-forming material preferably

should be a material which is removed by volatilisation during the
drying and/or firing operation such as powdered or granular
naphthalene, various organic resinous materials such as phenolic
resins or one which provides pores by reason of the generation of a
gas The resulting bodies, which have greater porosity than those made
with no pore formers, are particularly useful in the fabrication of
porous filtering media, catalysts and catalyst carriers, insulation
bodies and the like, whether in crushed granular form or in the form
of molded shapes of pre-determinedl contour.
The products can be made in any desired shape as well as provided in
granular or aggregate 'form They are, therefore, not only suited for
many of the uses for which industrial refractories are required,
including bricks, bldcks, setter tile, muffles, kiln furniture, and
special shapes for application in and around furnaces and other high
temperature equipment, but they are also well suited for many
specialty high temperature applications, such as jet engine combustion
chambers, linings for exhaust nozzles, rocket combustion chambers and
exhaust nozzles, turbine blades, stator blades and lens fusion blocks
They are also suitable for the fabrication of laboratory ware,
including combustion boats, crucibles, burner 70 holders, and other
shapes The bodies of the present inventions particularly when modified
by the use of pore formers in the raw batch from which the bodies are
made, are also highly useful as diffusion and filtering media, 75 such
as diffusion tubes and plates, filteringl tubes, plates and shapes, or
as catalysts or catalyst carriers and supports Materials and articles
of the present invention can, also be used for making abrasive
articles such as 80 grinding wheels, sharpening stones, razor hones,
and other grinding and polishing shapes and materials The present
bodies offer possible applications in the electrical and radio
industry including supports in electric light 85 bulbs, radio tubes,
X-ray tubes and radar equipment, resistors and grid leaks.
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* GB784706 (A)

Description: GB784706 (A) ? 1957-10-16
An improved fungicidal composition
Date of Application and filing Complete Specification: Sept 21, 1953.
784,706 No 25975153.
Index at acceptance:-Class 81 ( 1), E 1 C( 5 D:6:7 B:13).
International Classification:-A 611.
An Improved Fungicidal Composition I, AMERICO MOSCA, an Italian
Citizen, of 27, Via Carlo Boggio, Cuneo, Italy, do hereby declare the
invention for which I pray that a patent may be granted to me, and the
method by which it is to be performed, to be particularly described in
and by the following statement:-
The present invention relates to products used for fighting the
diseases caused in plants by fungi or vegetable parasites where it is
usually necessary to use Bordeaux mixture or other copper derivatives,
or barium, sodium, calcium polysulphides or zinc dithiocarbonates, and
the object of the invention is to provide a very efficient fungicidal
product to overcome said diseases which combines a very reduced cost
with a remarkably easy production.
Preparations employed for this purpose are already known, and depend
on the use of copper derivatives, as for instance, copper sulphate for
the basic component However, these preparations have the main
disadvantage of high manufacturing cost.
According to the present invention, it has now been found that
extraordinarily satisfactory results can be achieved by using a
Fungicide on the basis of Aluminium and its salts having as basic
component, aluminium powder or sulphate or other simple organic and

inorganic aluminium salts such as aluminium chloride, aluminium
nitrate or double aluminium salts which with the exception of
aluminium powder when dissociating in water will free aluminium ions,
some aids to adherence and dyeing substances being added in an
appropriate amount to said basic component.
An aid to adherence according to the present invention is a substance
used in the said mixture which has as its object to achieve a better
adhesion of the preparation to the leaves, and must present the
essential feature that it does not form insoluble compounds with the
aluminium sulphate if present, nor must it attack the aluminium
powder.
As substances aiding adherence of the type described, kaolin, talc,
bentonite or calcium sulphate may be used.
Furthermore, since the fungicide of the 50 invention is a limpid
solution having a light pink shade, it is necessary to add to the
composition a dyeing substance, such as methylene blue or malachite
green, which performs the function of showing where the composi 55
tion has been sprinkled during spraying operations.
When aluminium powder is used as the active ingredient of the
fungicide according to the invention, the fungicide is normally 60
used as a solid and water is not an essential ingredient, but can be
added when a medium to facilitate spraying is necessary.
When however the fungicide is prepared with aluminium sulphate and
like salts which 65 will free aluminium ions when dissociating water,
water becomes an essential ingredient which may be added before
application of the fungicide or if conditions are suitable the
fungicide can be used as a solid for the dis 70 infestation of the
soil against all kinds of fusarium in which case the water, necessary
for the dissociation of the aluminium ions, is the water as a rule
contained in the soil.
From the above it will be appreciated that 75 the fungicide according
to the invention will nonnally be sold as a solid and water will be
added when necessary by the user.
Since aluminium ores are widely spread all the world over in the
percentage of about 8 % 80 of the whole mass, the economic importance
of the discovery becomes apparent, when taking into account that the
soluble aluminium derivatives, when substituted for the copper salts
as a remedy against the common 85 plant diseases up to now fought by
said salts, present the advantage of being able successfully to fight
all the other plant diseases hitherto resisting the action of all the
other known fungicidal compounds, as the tomato 90 784,706 and
pepper-plant " Fusarium vasinfectum", the " Fusarium dianthi "
affecting the carnations and all the other " Fusarium" species which
cause heavy damages to the vegetables, flowers, bulbs or bulbous

plants, and to acid fruits, vines, cereals, mulberry-trees, potatoes,
cucumbers, pumpkins and melons.
Starting from 1921, both in France and in Italy the application of
aluminium derivatives in the form of aluminium sulphate added with
quick or slaked-Lime in the colloidal state was attempted, but the
results were useless.
Essentially, the invention resides in the fact that the aluminium
powder or stable aluminium derivatives which when dissociating in
water provided free aluminium ions, represent very efficient
fungicidal products, while the aluminium hydrate and oxide, under any
physical (colloidal or powder) form or structure, are not able to
avoid the sporule germination, due to their very poor water
solubility.
The use, as a fungicide, of aluminium sulphate, chloride or nitrate,
treated with slaked or quick-lime or with any other base, is
completely deprived of useful results, since these compounds produce
immediately aluminium hydrate which is substantially insoluble and
free from aluminium ions.
The action exerted by the sodium or potassium aluminates is very
limited in extent, since these compounds being unstable derivatives,
the atmospheric agents will form aluminium carbonate and,
successively, hydrate, thus strongly reducing the fungicidal power of
aluminates.
Excellent fungicidal results are also achieved by the use of double
aluminium and potassium salts (for instance: double aluminium and
potassium sulphate), that is by the use of double salts which, when
dissociating in water produce free aluminium ions.
Unsatisfactory results are produced by the use of organic compounds of
oxygen, which, although soluble, do not present free aluminium ions,
while aluminium organic derivatives (as for instance aluminium
acetate) which, dissociating, will free aluminium ions, have excellent
fungicidal features.
The results of Laboratory and field tests effected during two
consecutive years confirmed completely the power of the aluminium
powder or of aluminium derivatives having free ions to overcome plant
diseases.
Field tests were effected with a mixture, which in the following
descriptions is referred to as the standard mixture, having the
following composition:
6 o Aluminium sulphate 550 grams.
Bentonite 430 grams.
Methylene blue 2 grams.
Calcium carbonate 20 grams.
the mixture being diluted in 50-100 litres of water, when necessary to

free aluminium ions.
Addition of calcium carbonate is necessary in order to neutralise the
free acidity which, usually, accompanies commercial aluminium sulphate
since such acidity is harmful to some plants, even if present in very
reduced amount 70 (as for instance 1 part per 10 000).
The experiments were effected on a very great number of plants for a
duration of two agricultural years giving excellent results.
As an example: the test was effected on 75 30,000 pear and apple trees
of every type:
on 10,000 peach trees of every type: on 50,000 vine plants (of the
-barbera".
" dolcetto", " freisa", -nebbiolo", " barbaresco", "muscat", "
ripening in July " 80 types and of assorted types); on 200,000
pepper-plants of every type, on 20,000 tomato plants of every type, on
250,000 potato plants of every type; on 400,000 carnation plants of
all the best praised varieties including 85 " valentine " and "
minerva"; on 100,000 rose-bushes, bulbs and bulbous plants,
chrysantema, ornamental plants and so on, and also on cereals,
spinach, asparagus, onion, celery, pumpkin, apple, cucumber, water 90
melon plants and on nursery beech trees.
In none of the experiments did the fungicide exhibit any toxicity, and
a flourishing vegetation with excellent crops was observed.
In effect, since the aluminium sulphate 95 mixtures are provided at a
p H value equal to that of the plant lymph, the result is the
absorption of aluminium with subsequent formation of proteinate which
acts as a catalyst, thus favouring the attainment of an 100 excellent
crop.
The accurate examination of the produce obtained with the aid of the
novel fungicide allowed a premature or earlier ripening and a better
crop than that obtained by plants 1 oa treated with other fungicidal
mixtures.
It will be noticed that the preparation according to the invention is
positively harmless and non-toxic to the plants, while it appears to
be also harmless and non-corrosive 110 for the farm-tools.
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* GB784707 (A)
Description: GB784707 (A) ? 1957-10-16
Improvements in integrators for computing the mean value and other
characteristics of voltages derived from electrical testers
Inventor: JOHN LIGHTFOOT SPENCER-SMITH Date of filing Complete
Specification: Oct 8, 1954.
Application Date: Oct 9, 1953.
No 27763/53.
1 Complete Specification Published: Oct 16, 1957.
Index at acceptance:-Class 37,,G 2 B( 1: 2: 4: 6), G 3 A( 3: 6).
International Classification:-G 06 g.
Improvements in Integrators for Computing the mean Value and other
Characteristics of Voltages Derived from Electrical Testers We, LINEN
INDUSTRY RESEARCH ASSOCIATION, of The Research Institute, Lambeg,
Lisburn, County Antrim, Northern Ireland, a body corporate organised
under the Laws of Great Britain, do hereby declare the invention, for
which we pray that a patent may be granted to us, and the method by
which it is to be performed, to be particul 3 arly described in and by
the following statement: -
This invention relates to inmprovements in integrators for computing
the mean value or other characteristics of voltages derived from
electrical testers.
The integrator circuit may be employed to give statistical information
about any quantity the variations of which form a mean value can be
expressed as a varying voltage.
An integrator is described in the specification,of Patent No 681,447
which claims a method of determining the mean deviation of the
variable quantity of substance in the cross-section of slivers,
rovings or yarns from its average value, characterised in that an
equivalent electrical current is first obtained from said variable
quantity of substance in the cross-section, the average value of this
electrical current being separated from its deviations from the
average value with the aid of an electrical frequency-dependent

filter, including 'a pair of input and two pairs of output terminals,
the first pair of output terminals supplying an electrical direct
current equivalent to the average value of the quantity of substance
in said cross section, the second pair of output terminals supplying
fan electrical alternating current equivalent to the deviation value
from the average value of said quantity of substance in the
cross-section, said alternating current being rectified by means of an
electrical rectifier, and the output direct current of said rectifier
which is equivalent to the deviation value of the variable quantity of
lPrice 3 s 6 d l said substance from its average value, being averaged
by means of at least one electrical capacitor connected in series with
at least one electrical impedance and then the averaged direct current
equivalent to the mean deviatifon of said variable quantity of
substance in the cross section being made visible in an electrical
measuring instrument.
The integrator described in specification
No 681,477 is substantially as shown in Fig.
1 of the accompanying drawings 'and consists of a full wave rectifier,
2, providing a voltage which is proportional, either to the rectified
value of the voltage output of the yam or sliver tester 1 or to the
square thereof, connected in series with a resistance, 3, and a
condenser 4, which is connected in parallel' with a high resistance
voltmeter or similar device S for measuring voltage, so that the
voltage registered by the voltmeter represents an average value of the
rectified values of the applied voltages or to the squares thereof.
This integrator performs two distinct functions: (a) it converts
the;alternating voltage from the tester into a direct voltage, (b) it
provides a relatively low impedance circuit for charging the condenser
compared with the relatively high impedance of the discharging circuit
and so provides a greater time constant for discharging the condenser
than for charging it.
The response of the integrator to a deviation in the size of the yarn
or sliver, therefore, depends upon whether it is greater or less than
the average deviation as indicated by the voltmeter; when a deviation
in the size of the yarn or sliver is greater than the value indicated
by the voltmeter, the response of the integrator is disproportionately
greater than when a deviation is less than the value indicated by the
voltmeter, which consequently indicates 'a biassed average which is
greater 784,707 2 784,707 than the actual value of the meai or of the
mean squared deviation mean size of the yarn or sliver.
The values of the time constants, for charging and discharging the
respectively, can be expressed mat in terms of the values of the corn
follows: RV(R, R + R,-) T, = C x sec.
R, + R + R, + Rx and T 2 = C x R, sec.

where C is the capacitance of the cond Rv is the resistance of the
vltm R, is the resistance of the resist R 'is the forward resistance
of the rectifier 2, and R, is the output impedance of th or electronic
yarn and sliver i tester 1.
From this it follows that T, must less than T.
When a varying voltage v, whi( portional to the deviations in size
sample, is fed from the tester into tor which contains a linear
rectifier meter fluctuates about a mean voltag given by:
R.Rv R+Rs+Rs where l is the solution to the eqt J(t-u) F(,) Am cc CV
and F (v) is the frequency distribut varying voltage, supplied by the
tes When T = T, the value of v obt equation ( 3) is equal to the Mean
of the variations in the output of but when T 1 is less than T, the
will be greater than the mean devia amount which depends both on th
T./T 1 and the form of the frequ tribution.
When T is equal to or greate times T,, the bias becomes so gre n
deviation effectively becomes an average of the larger from the
deviations only-i e deviations which exceed a value determined by the
bias and thus by T 1 and T the ratio T,/T,-and approximates to half
condenser of the mean range as defined, there bring hematically only a
certain small probability that any deponents as viation will lie
outside this range.
Values of T 2/T, equal to 80 or 1,370 are preferred because, with
deviations which follow a normal frequency distribution, the in( 1)
tegrator indicates a mean range which can be defined as the value
which is exceeded by approximately 5 per cent or 0 1 per cent of ( 2)
the deviations, respectively Similar considerations apply when the
rectifier provides a current which is proportional to the square of
tenser 4, the deviations in voltage supplie d by the aeter 5, tester.
ance 3, Therefore measurements of the mean devia e full wave tion and
the mean squared deviation by the said integrator are subject to
errors, whose e electrical magnitude depends both upon the ratio of
irregularity the time constants, T /T,, and the form of the frequency
distribution of the sizes of always be short lengths of the sliver or
yarn, the correct values of the mean and mean squared dech is pro
viations being only obtained when the time along the constants T, and
T are equal.
an integra The invention comprises an integrator for the volt
measuring the mean value or the mean squared ge which is value of the
output of electrical testers in which the tester feeds a
capacitor-charging circuit and a measuring instrumnent through a
control unit, which comprises a rectifier and a pair of electronic
valves whereby the said control unit isolates the capacitor-charging
circuit from the tester and delivers tce the uation:
capacitor-charging circuit a voltage which is proportional to the

rectified output of the tester or to the square thereof, and whereby
the time constants for charging and discharging capacitor-charging
circuit are made equal.
The invention further comprises an integrator for measuring the mean
of the values of the range or the mean of the maximum or minimum
values of the variations which occur in equal consecutive prescribed
intervals of ,3 time in the output of electrical testers in which the
tester feeds a capacitor-charging circuit through a control unit which
comprises a pair of electronic valves and a rectifier in ion of the
series with a variable resistance, whereby the ter time constant of
the capacitor-charging circuit ained from may be adjusted ito give a
prescribed ratio of Deviation the time constants; for discharging and
chargthe tester, ing the capacitor circuit.
value of v In an application of the invention where tion by an the
integrator measures the mean squared e ratio of value it contains a
linear rectifier and a rectiency dis fying and controlling unit which
serves the dual purpose, firstly of squaring the tester outrthan 30
put, and secondly of permitting the time coneat that, stants, T, and
T, for charging and discharg8 C 784,707 784,707 3 ing the circuit to
be equal.
When the integrator is intended for measuring the mean of the values
of the range of the deviations there is introduced into the Integrator
circuit, a rectifying and controiling circuit, which allows the time
constant T,, for charging the condenser, to be varied independently of
the time constant T 2, for discharging the condenser, so that the
ratio T 2/T 1, is made at least 30 to 1 and the integrator indicator
sensibly responds only to comparatively large signals and indicates
'an average value of their larger deviations The preferred ratios of
the time constants To/T 1 are 80 or 1,370 so that when the output
signals follow the normal frequency distribution, only approximately 5
per cent or 0 1 per cent, respectively, of the signals exceed the
value indicated by the integrator.
For measuring the average or mean values of the maximum and minimum
values of the variations which occur in equal consecutive prescribed
intervals of time a similar arrangement is employed to that for
measuring the mean of the values of the range with the exception that
the full wave rectifier is replaced by a half wave rectifier, which is
arranged to pass only currents which correspond either to positive
deviations in the signals for measuring the average of the maximum
values of the sgnals or to negative deviations in the signals for
measuring Ithe average of the minimum values of the signals.
For measuring these average of the maximum and minimum values of the
variations of the signals respectively the time constant T 2 for
discharging the condenser is at least 30 times greater than the time

constant T, for charging the condenser, land the preferred values of
the ratio are 80 and 1,370.
In order that the invention may be fully understood it will be more
particularly described with reference to Figs 2 to 5 of the
accompanying drawings, Fig 1 of these drawings being the integrator
previously described as being the kind described in specification
681,477 In these drawings: Fig 2 is a diagram of a preferred circuit
of an integrator for computing the mean value in which the time
constants T, land T, for charging and discharging the condenser are
made equal by means of a rectifying and controlling circuit.
Fig 3 is a diagram of a circuit of an integrator for computing the
mean squared value in which the time constants T, and T, for charging
and discharging the condenser are made equal by means of a rectifying
and controlling circuit.
Fig 4 is a diagram of a circuit of an integrator for measuring the
mean of the values of the range of the variations in such a way that
the time constant T 1 for charging the condenser is at most 1/30th of
the time constant T, for discharging the condenser, and Fig 5 is a
diagram of an integrator for measuring average values of the maximum
or minimum values of the variations of the signals.
In the diagram shown in Fig 2 of the circuit of an integrator for
computing the mean value in which the time constants of the circuit T
1 and T 2 for charging and discharging the condenser are made equal by
means of a capacity changing circuit ior rectifier and control unit
consisting of a rectifier 2 followed by a cathode follower stage,
which effectively isolates the rectifier 2 from the condenser 4, an
electrical or electronic yarn and sliver regularity tester, 1,
provides an output voltage which is proportional to the deviations
about the mean of the weight per unit length of the material being
tested, the output voltage being fed through the linear full wave
rectifier, 2, to the grids of two electronic valves, 6 land 7, which
are operated as cathode followers having equal cathode resistances 8
and 9 The cathodes of the valves, 6 and 7 are connected through a
resistance 3 to a condenser 4, which is connected in parallel with a
high resistance voltmeter 5.
The operation of the circuit is as follows:the rectified signal from
the rectifier 2 induces a voltage between the cathodes of the valves 6
and 7 which is fed to the damping circuit consisting of the resistance
3 the condenser 4 and the high resistance voltmeter 5, which registers
the mean deviation of the variations.
The time constants of the circuit T, and T.
for charging,and discharging the condenser are both equal and given by
R 1 x R, Tl=T=C x Rz + R where R, and Rv are the resistances of the
resistance 3, and the voltmeter 5 respectively 105 and C is the

capacity of the condenser.
An integrator circuit for computing the mean squared value may be the
same as that shown in Fig 2, but using a square law instead of a
linear rectifier 2 Fig 3 shows an 110 alternative form of integrator
circuit for computing the mean squared value In this arrangement the
output voltage from the tester 1 is fed through a rectifying and
controlling unit 10 comprising a full wave linear 115 rectifier 2 and
a known type of voltage squaring circuit, the output of which is fed
through a resistance 3 to a condenser 4, which is connected in
parallel with a high resistance voltmeter 5 The rectifying 'and
controlling 120 circuit serves two purposes, firstly, it provides a
current which is proportional to the square of the rectified values so
that the integrator averages the squared values, and secondly it
effectively isolates the tester 1 from the con 125 denser 4, and
equalises the time constants T 1 784,707 and T, for charging and
discharging the condenser, and the reading on the voltmeter 5 is
therefore proportional to the mean squared value Fig 4 shows an
integrator circuit for measuring the mean of the ratios of the range
of the variations in which the circuit shown in Fig 1 is modified in
such a way that the time constant T, for charging the condenser is tat
most 1/30th of the time constant, T 2 for discharging the condenser,
the preferred values of the ratio, T 21/T 1 being 80 and 1:370 as
already stated In Fig 4 the output voltage from the tester 1 is fed
through a rectifying and controlling circuit 11, consisting of two
electronic valves 12 and 13, operated as cathode fllowers a variable
resistance 14 and a full wave linear rectifier 2 The cathode followers
12, 13 are operated in such a way that the output impedance of the
unit 11 is kept small The output from the cathodes of the valves 12
and 13 is fed through the variable resistance 14 'also included in the
control unit, to the full wave rectifier 2, which should preferably
consist of diode valves, having a low resistance to current passing in
the forward direction and a very high resistance tc current passing in
the reverse direction The output from the rectifier is fed to the
condenser 4, which is connected in plarallel with a very high
resistance voltmeter 5 With such arrangement the time constant T 1 of
the circuit for charging the condenser depends sensibly upon the
capacity of the condenser 4, output impedance of the cathode follower
stage 12 and 13, the forward resistance of the rectifier 2, and the
resistance 14 and may therefore be varied over a wide range by means
of the variable resistance 14 The time constant T of the circuit for
discharging the condenser depends upon the capacity of the condenser
4, and the resistance of the voltmeter and is very much greater than
T, The integrator is adjusted by varying the resistance 14 in the
control unit until the ratio of the time constants T,/T 1 has the

desired value.
Fig 5 shows an integrator circuit, for measuring averages of the
maximum or minimum values corresponding respectively to the positive
and negative larger deviations in the SO signals from the tester The
circuit is identical with that shown in Fig 4 with the single
exception that the full wave rectifier 2 is replaced by a half wave
rectifier 15, which is arranged to pass only currents which correspond
either to positive deviations in the sig 55 nal for computing the
average of the maximum values of the variations of the signal, or to
negative deviations in the signal for computing the average of the
minimum values of the signals The other components CO are the same as
those described ill Fig 4 and as previously described the resistance
14 is used to adjust the value of the time constant T for charging the
condenser until the ratio of the time constants TI/T, has the de 65
sired value, which should be at least 30 and preferably 80 or 1370.
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