Note: Descriptions are shown in the official language in which they were submitted.
~ 3 ~i35B9
- 1 -
SPEC IF ICATION
RUBBER ~SIIEET FOR T~JRNTABLE
TECHNICAI. FIELD
This invention relates to a rubber sheet for
record player turntable.
BACK(~RnlJND ART
The function of such a rubber sheet is to
isolate a disk record from acoustic outpu~s from a
speaker, vibrations o a record player itself, etc.
and prevent howling and deterioration o SN ratio due to
vibra~ions of the disk record during reproduc~ion. The
howling is a sort of oscillation due to an acoustic
feedback of outputs from a loud speaker to the pickup
assembly and occurs mainly due to the vibrations of the
speaker which are transmitted to the record player via
the floor or rack where the record player is mo~lnted, or
- 20 due to the direct vibrations of the record player caused
by a sound pressure from the speaker. Of course, the
normal condition of playback of the disk record cannot be
expected when the hol~ling occurs. Even where no howling
takes ~lace, the frequency response of the pickup
assembly would be altered and the local resonance would
be caused by such external vibrations, and the increase
Of cross-modulation distortion9 the deterioration of
transient phenomena, etc. would affect adversely the tone
qualitv of reproduced sounds. As stated above, howling
takes place mostly due to external vibrations from the
floor or rack where the record player is mounted. The
majority of such external vibrations is of the order less
than l~0 Hz and particularly includes a superlow
frequency component of approximately 5 to lQ Hz. To
provide for an effective inhibition of howling, a rubber
sheet for turntable which exhibits excellent vibration-
damping pro~erties in such superlow frequency region is
desirable.
., . '3~.
~ :~ 635~
- 2
The conventional rubber sheets ~or turntable
which typically com~rise natural rubber, isoprene rubher,
chloroprene rubber, butyl ruhber, styrene-butadiene
rubber, butadiene rubber, silicone rubber or urethane
rubher alone or in combination, however, are inferior in
vibration-damping properties especially in the superlow
frequency range, and are unahle to protect effectively
the tone ~uality of reproduced sounds from deteriorating
due to howling or ex~ernal vibrations.
DISCLOSURE OF INVENTION
The inventor has devoted extensive and
thorough efforts to the development of a new rubber sheet
for turntable which effectively inhibits the tone quality
of reproduced sounds from deteriorating due to howling
or external vibrations and permits reproducing source
sounds (for example, human voices themselves) as
faithfully as possible. As a result, it has been found
that the above described object can be achieved by a
sheet~ e cured rubber molding having a hardness between
30 as measured with an A-type rubber hardness tester
and 15 as measured with an F-type rubber hardness tester
and an impac~ resilience of not less than 40 ~.
In the foregoing, the term "A-type rubber
hardness ~ester" is used to mean a ruhber hardness
- tester which conforms to JIS K 6301-1969. Further, the
F-type rubber hardness tester implies Asker-F type
rubber hardness tester bv Kobunshi Keiki Mfg. Co., Ltd.
which is o~ten used for measurements of
hardness of foam rubber, urethane foam or the li~e.
Although being solid rubber, some of the cured ruhber
used in accordance with the present inven~ion is too low
in hardness to measure by means of ~he A-type rubber
hardness tester which is of use in measuring hardness of
conventional solid rubbers. To this end, the lower
limit of hardness of the cured rubber used in accordance
with the present invention is defined by one as measured
with the P-type rubber hardness tester.
~ ~ 6~9
- 3
An intermediate hardness range between the
measuring range of the A-type rubher hardness tester and
that of the F-type rubber hardness tester may be measured
with a C-type rubber hardness tester. The term "C-type
rubber hardness tester" as used herein means one ~hich
meets the Society of Rubber Industry Japan Standard
SRIS-0101 and is widely used to measure such intermediate
hardnesses between the measuring ranges of the A-type
and F-type rubber hardness testers. The C-type tester
is mostly used to measure the hardness of sponge7 soft
rubber or the like. As the C-type rubber hardness
tester, Asker-C type rubber hardness tester by Kobunshi
Keiki Mfg. Co., Ltd. is used in the present invention.
If the situation permits, any of these A type,
C-type and F-type rubber hardness testers may be used to
determine the hardness of cured rubbers for the purpose
of the present invention. However, if hardness is less
than 1 when the A-type rubber hardness tester is in use 9
it is preferable to measure hardness with either the
C-type ruhber hardness tester or the F-type rubber
hardness tester because measurements with the A-type
hardness tester accompany încreased errors. Similarly,
if hardness is less than 1 for the C-type hardness
tester, it is more desirable to use the F-type hardness
tester in connection with hardness measurements.
Furthermore, in the case ~hat hardness is more ~han 99
for the C-type hardness tester, it is preferable to use
the A-type rubber hardness tester. In the case that
hardness is more than 99 for the F-type hardness tester,
it is also preferable to use the C-type hardness tester
or the 4-type hardness tester. Hardness values measured
with the A-type, C-type and F-type rubber hardness
testers will hereinafter be referred to as "A hardness",
"C hardness" and "F hardness", respectively.
The cured rubber employed in accordance with
the present invention bears a hardness of not more than
3n, preferably not more than 20 in A hardness to no~
less than 15, preferably not less than 30 in _
.~ ~ ;1 83569
- 4
hardness and exhibits an impact resilience of not less
than 40 ~7 ~ preferably not less than 50 %, most preferahly
from 60 to 9S ~. Such a cured rubber is a new rubber
material which has not been known in the art. In other
words, cured rubbers with an A hardness of not more than
about 30 is known but they show an impact resilience of
less than about 40 %, and those with an impact resilience
of more than about ~0 ~ have an A hardness of more than
about 3n. It is common knowledge that impact resilience
of cured rubber declines with a decrease in its hardness.
The physical properties of the cured rubber of the
present invention, i.e. an A hardness of not more than
30, preferablv not more than 20, and an impact
resilience of not less than 40 %, preferably not less
than 5n ~ ~ most preferably from 60 to 95 %, are definitely
outside of the prior common concept.
In accordance with the present invention, the
rubber sheet for turntable comprising the above
described new and unique cured rubber has the remarkable
advantages of sho~-ing excellent vibration-damping
properties especially in superlow frequency range and
pre~enting the tone quality of reproduced sounds from
deteriora~ing due to howling or external vibrations.
This rubber sheet effectively absorbs and shields off
vibrations of superlow frequency9 typically those less
than 10 Hz, and isolates a disk record from these
vibrations, thus inhi~iting howling with no likelihood of
pickup outputs being modulated with these vihrations. As
a result, listeners can enjoy excellent reproduced sounds
over the broad range from ~reble sounds such as the
soprano of female vocal sounds to bass sounds with
enriched im~ressions of presence when they play back
disk records.
For the cured rubber of ~he present invention,
it is necessary that the hardness ranges from an A
hardness of not more than 30, preferably not more than
2n to an F hardness of not less than 15, preferably
not less than 30 and the impact resilience is not less
,.
S 6 9
- 5
than 4~ ~, preferably not less than 50 ~ most preferably
from 60 to 95 ~. The cured ruhber can exhibit excellen~
vibration-damping properties especially in ~he su~rlow
frequency range and prevent the tone qu~lity of
reproduced sounds ~rom deteriorating due to howling or
external vibrations with maintaining the general
properties as a rubber shee~ for turntable, when the
hardness and impact resilience fall within the above
defined ranges. If the hardness is higher than the above
definition and the impact resilience is lower than the
above defini~ion, the vibration-damping properties
become poor especially in the superlow frequency range
and the soft and elastic characteristics of the cured
rubber like baby s~in which is one of the significant
features of the present invention, become lost.
Furthermore, the rubber sheet does not come closely in
contact to nor stick to the disk record or turntable,
nor does it ensure a desirable breathing phenomenon
thereabove and below (this will be discussed later~.
If both hardness and impact resilience are below the
above specified ranges, the rubber sheet has only a
scarce self-supporting property and can not undergo the
weights of a disk record, a cartridge and a pickup arm,
resulting in exhibiting substantially no elasticity.
~lore particularly, the projections which are preferably
provided on the rubber sheet as described later become
deformed and flat, resulting in increase in the contact
surface area between the rubber sheet and a disk record
or turntable. As a result, the reproduced sounds tend
to become heavy and it is difficult to reproduce clear
and steady source sounds in a range including both
treble and bass regions.
The rubber sheet of the present invention can
be classified into the following three categories,
depending on its physical proPerties, mainly on the
basis of differences in hardness:
Category (I!: Hardness is from more than 15
to not more than 3n in A hardness and impact resilience
~ 3 6355~
~ fi
is not less than 50~, particularly from 65 to 95%. The
rubber sheet of ~his category peTmitS especially sounding
sounds to be reproduced. Consequently, for example,
sounds of a pipe organ or soprano of female vocal sounds
can be reproduced as faithfully as possibl~.
Ca~egory (II): Hardness is from 1 to 15,
preferably from 2 to 7 in A hardness and impact
resilience is from 40 to 95 ~, more preferably fTOm 50
to 9S ~, most preferably from 60 to 95 %. The rubber
sheet of the category (II~ enjoys the advantages of bo~h
of the rubber sheets belonging to the category (I) and
category ~ discussed below.
Category (III): Hardness is from less than 1
in A hardness to not less than 15, preferably not less
than 3~ in F hardness, and impact Tesilience is not
less than 4~ ~, more particularly 5~ to 95 %. The rubbeT
sheet of ~his category effectively inhibits howling and
permits reproducing excellent sounds of superlow
frequencies.
It is further desirable that, in addition to
the above defined physical properties, the cured rubbeT
. in accordance with the present invention bears a tensile
- strength of 0.1 to 100 kg./cm2, more preferably 1 to 50
kg./cm29 an elongation of 50 to 1,000 ~, more preferably
200 to 1,000 ~ and a specific gravity of 0.8 to 1.3,
` more preferably 0.89 to 1.05. If the tensile strength
is less ~han the above definition, the rubber sheet
shows a scarce self-supporting property and becomes
fragile and easily broken upon application of small
tensile foTce. ContraTily, if i~ is greater than the
above difinition, the rubber sheet becomés less flexible
and fails to come closely in contact ~o or stick to the
disk record or the turntable. The breathing as stated
above is difficult when the elongation is .smaller than
the above range and the rubber sheet becomes rather
extended to the maximum and sagged when it is greater
than the specific range. When the specific gravity is
greater than the above range, an excess load is applied
3 ~ 6~9
to a driving motor for the turntable, provided that the
average thickness of the rubber sheet is greater than 2
mm., thus amplifying vibration sounds from the motor.
On the other hand~ when the specific gravity îs less
than the above range, it b~comes impossible to add
fillers to ~he rubber composition, with the result that
the rubber sheet will have only a scarce self-supporting
property.
Preferred physical constants for rubber sheets
of the above-defined categories (I), (II) and (III! are
as follows:
Category (I)
Tensile strength: 1 to 100 kg./cm.2, particularly 5 to
50 kg./cm.
Elongation: 100 to 1,000 %, particularly 200 to
1, 000 ~
Specific gravity: 0.89 to 1.05
Category (II~
Tensile strength: 1 to 50 kg./cm.2, particularly 3 to
50 kg./cm.2
Elongation: 100 to 1,000 ~, more preferably 120
to 1,Q00 ~, and most preferably 200
to 1,000 %
Specific gravity: 0.89 to 1.05, particularly 0.93 to
l.Q5
Category (III)
Tensile strength: 0.1 to 50 kg /cm.2, particularly 0.1
~o 20 kg./cm.
Elongation: ln0 to 1,0n0 %, particularly 200 to
1,000 ~
Specific gravity: 0.8~ to 1.05
The cured rubber having the above specific
physical constants is obtainable by curing a rubber
composition which comprises (Al 100 par~s (parts by
weight, the same hereinafter) o~ a rubber component, (B!
1 to 2,00n parts of factice (preferably 5 to 2,000 parts
and most preferably 100 ~o lyS00 parts) and ~C? 20 to
2,000 parts of a softening agent (preferably 5q to 2,000
-
p~rts and most preferably 200 to 1,5~ parts~. The
rubber composition containing such large a~ounts of a
factice and a softening agent is a new rubber composition
from which a particular cured rubber having a hardness
of not more than 3~, particularly not more than 20
in A hardness and an impact resilience of no~ less than
40 %, preferably not less than 50 %, most preferably from
60 to 9S % is available by cuTing.
The rubber component (A~ may include, without
limiting thereto, one or mOTe components such as
polynorbornene, natural rubber, isoprene rubber,
chlo~oprene ruhber, styrene-butadiene rubber) butadiene
rubber, butvl rubber, ethylene-propylene rubber 9
ethylene-propylene-diene rubber, nitrile rubber, acryl
rubber, urethane rubber, chlorinated polyethylene,
chlorosulfonated polyethylene, epichlorohydrin rubber,
polysulfide rubber, silicone rubber and the like as a
- predominant componen~. These components may include
regenerated rubber (for example, rubber powder OT the
like) thereof. Furthermore, these rubber components may
be either in the form of solid (powder, pellet, block,
sheet, etc.~ or in the form of liquid (liquid rubber,
latex, etc.l. Out of these components~ a Tubber
component composed of polynorbornene as a predominant
component is most favorable for the purpose of the
present invention. In that case it is desirable tha~
polynorbornene accounts for 50 ~ or more (percen~ by
weightg the same hereinafter) of the total weight of the
rubber component and more preferably 65 % or more.
Preferably, polynorbornene used herein has an average
molecular weight of about 106 to about 5 X 106 and more
preferably about 2 X 106 to abou~ 3 X 106.
The f~ctice as the component (B3 may include
any of various kinds of factices such as white factice,
dark bro~ factice~ amber factice and blue factice
which are available by vulcani~ing a variety of vegetable
3ils including L~eed oil, rapeseed oil, soybean oil,
sesame oil, tung oil and castor oil with use of sulfur or
1 .~ 63569
~,
sulfur chloride. Those factices may be used alone or in
ad~ixture. The factice prepared by vulcanizing rapeseed
oil is mos~ favorable.
The softening agent as the component (C~ may be
oils, plasticizers or other agents having a softening
activity. The oi~ used herein include aromatic oils,
naphthenic oils, paraffinic oils, ~egetable oils and
animal oils which are commonly used as a filling oil
(softening oil, process oil, e~c.l in rubbers. The
vegetable oils and animal oils mentioned abo~e include
castor oil, rapeseed oil, linseed oil, whale oil, fish
oil and the like. Out of plasticizers widely used fOT the
manufacture of rubbers9 those having a high softening
performance, e.g., dibutyl phthalate, dioctyl phthalate
and dioctyl sebacate may be used for the purpose of the
presen~ invention. Other softening agent includes liquid
rubbers. Of course, these softening agents may be used
alone or as a mixture. As a rule, oil alone or in
mixture with such a plasticizer is recommended.
~loreover, those widely used rubber ingredients
including fillerc such as carbon black and zinc oxide,
colorants, lubricants such as stearic acid and
~ antioxidants may be properly added to the rubber
;~ composition to the ex~ent that they do not impair the
above-discussed physical properties, in addi~ion to the
components ~A! to ~C~.
Preferred rubber compositions for the rubber
sheets of the categories ~I~ to (III! are as follows:
Category (I~
Component (A1 100 parts
Component (B~ 1 to 1,500 parts, preferably 5 to l,OOn
parts and mos~ preferably lOQ to l,nOO
parts
Component (C~ 20 to 1,50Q parts, more particularly zon
to 1~000 parts
Category (II !
Component ~A~ 100 parts
Component (B~ 5 to 1,500 parts, preferably 20 to 19 500
``1~
~ ~ 63~g
.
parts and m~st preferably 1~0 to 1,000
parts
Com~onent (Cl sn to 19500 parts, more particularly 200
to 1,000 parts
5 categOry (III~
CoJnpo n en t ~A ~ l O û parts
Component (B) 20 to 2,0~0 parts, preferably 50 to 1,500
parts and most preferably 100 to 1, S00
parts
: 10 Component (C) 50 to 2,000 parts, preferably Z0~ to
1, 500 parts
The above rubber composition can be cured by
any one of conven~ional curing methods including sulfur
curing and sulfurless curing. Curing can be ca~ried out
under normal conditi~ns without any specific limitations.
A typical example of the rubber composition,
in the case of sulfur curing, is as follows:
(Component ! (Parts)
Rubber lOn
Factice 1~0 to l7~no
Sotening agent 2~0 to l~son
Filler 1 to 200
Antioxidant 07 5 to 6
Sulfur 0.5 to 10
- 2~ Curing accelerator 1 to 20
As ano~her significant feature of the ~ubbeT
sheet for turntable in accordance with the present
invention, there is no need for after-treatments, e.g.
halogenation and coating as -experienced with the prior
art rubber sheet for turntable, with the ormer ensuring
increased surface hardness to make the rubber sheet not
susceptible to scratches and the latter preventing
deposit of dust. l~ile being very low in hardness as
set forth above, the rubber sheet for turntable in
accordance with the present invention is high in impact
resilience, resulting in less or no scratch or dust
thereon. Even where the rubber sheet is scratched or
dust is attached on the Tubber sheet, it is very
.
1 ~ ~35~
convenient to re~ove such scratch or du.st, if the rubber
sheet is swung or crumpled with ease like cloth since
it is very soft and flexible. Unlike the prior art
rubber sheets, the ruhber sheet of the present invention
has another surnrising advantage that washing in water is
suitable for cleaning and the rubber sheet can be cleaned
by washing with crumpling.
The rubber sheet for turntable in accordance
with the present in~ention is subjected to no particular
limitations as to configuration and may be, in principle,
of any well-known configuration. Nevertheless, the
following c`onfigurations, combined with the above
discussed physical properties, ensure a further
improvement in vibration-dam~ing properties and tone
quality.
In other words, a preferable configuration of
the rubber sheet for use with turntable in accordance
with the present invention includes a large number of
projections on a major surface of its disk-shaped sheet
body.
Since a turntable or a disk record contacts
the turntable rubber sheet only atop the projections,
the contact area is only a minimum and external
vibrations are hardly transmitted to ~he disk record.
Furthermore, the turntable rubber sheet with the above
configuration provides a unique advantage as follows:
~ t is generally known that ~he substance
with the smallest velocitv of sound is rubber and that
with second smallest velocity of sound is air. When the
rubber sheet with the above specific configuration is in
contact with the turntable, a thin layer of air is
;~ confined between the rubber sheet and the turntable due
to the projections so that air in this layer moves
inwardly and outwardly through respective ones of the
~rojection-to-~rojection s~aces during the revolution of
the turntable, as if the human being breathes.
Consequently, the rubber sheet and the disk record
thereon can be regarded as resting on air. This
i ~ ~35~9
- 12 -
insures complete isolation of the external vihrations
and an improvement in tone quality~ Similarly, in the
case where the rubber sheet with the specific configuration
is in contact with the disk record, the foregoing
situation is envisaged between the rubber sheet and the
disk record. As is obvious from the foregoing, the
above con-figuration effectively shields off vibrations
of a superlow frequency of the order less than 10 Hz and
prevents these vibrations from being transmitted to the
disk record, thus inhihiting howling with no likelihood
that pickup outputs would be modulated with these
vibrations.
While the projections in the above specific
configùration of the rubber sheet may be of various
shapes without any particular limita~ions, it is
preferable in order to minimi~e the contact area with
the turntable or the disk record that the area of each
head of the projections be as small as possible. To
this end at least the head of each of the projections
is ridge-shaped to make substantially a line contact
with the turntable or the disk record. For example, the
projections may be roof-shaped, semicircular in section
or particularly knife edge-shaped. Another desirable
projection has at least such a pointed head as to make
substantially a point contact with the turntable or the
disk record. The latter shape may include a pyramid
(including a polvgonal pyramid, e.g. a triangular
pyramid, a quadrangular pyramid and so on, the same
hereinafter~, a cone (including an elliptical cone, the
3~ same hereinafter~, a dome (including a near sphere, a
hemisphere, a column with a rounded upper portion and the
like, the same hereinafter~ and the like. Preferably,
each of the latter projections has such a sharp head
as a needle. For each of the projections with the two
different kinds of shape, it is necessary that at least
the head thereof be ridge-shaped or pointed with no
particular requirements as to the root thereo~. For
example, it may comprise a root of a head-free pyramid
~ 1 ~3~6~
a head-free cone, etc. and a head having a roof shape,
semicircular shape, a pyramid, a cone, a dome, etc.
Furthermore, other shapes (e.g. head-free pyrmaidal,
pillar-shaped or column-shaped projections~ are available
S as long as the contact area with the turntable or the
disk record is held as small as possible. It is also
obvious that these projections may be provided at its
top with small recesses to ensure line contact or point
contact.
It is preferable ~hat the contact area between
the projection-bearing surface and the turntable or the
disk record be 0.01 to 10 % of the entire area of a
major surface of the rubber sheet (i.e. the area of a
circle having the same diameter as that of the rubber
sheet, the same hereinafter~ and more particl~larly 0.01
to 1 ~.
Preferably, the height of the projections is
~.1 to 5 mm. and more particularly 0.3 to 1.8 mm~
Failure to meet this criterion results in difficulty for
the air-breathing behavior as mentioned above.
The projections may be formed on the body of
the ruhber sheet regularly or at random. Regular
alignments may be concentric, spiral, radial, etc. The
individual projections may be either spaced at an
appropriate interval or closely aligned in contact with
one another. When these projections are closely aligned,
the adjacent projections may be connected integrally with
each other at their roots (as ribs are concentrically
aligned on the body of tlle rubber sheet together with
closely spaced recesses in the case where the projections
are closely aligned in concentric arrays~. Pre~erably,
the projections are closely aligned in concentric arravs
or the like so that alignments o~ the projections hold
air in a space between the rubber sheet and the turntable
or the disk record. With this arrangement, the air
involved therein passes through the gaps between the
closely aligned projections, thus providing better
breathing behavior and further improvements ln vibration-
~ 1 ~35~9
.
- 14 -
damping properties and tone quality of reproduced sounds.
The projections may be formed integrally with
the rubber sheet, or formed separately from the rubber
sheet and affixed thereto by a conventional technique
such as bonding.
Although the rubher sheet of the above specific
configuration has the projections on the one major
surface, the other major surface of the rubber sheet is
free of particular limitaitons as to configuration. For
example, the other major surface may be completely flat
or bear the same projec*ions as set forth above or bear
concentric, spiral or radial grooves or ribs. Large
recesses or projec~ions each having a circular shape, a
polygonal shape in plan view may be aligned regularly
(e.g., concentrically, spirally or radially) or at
random.
Preferred configurations of the rubber sheet
for turntable in accordance with the present invention
will now be discussed by reference to the drawings.
BRIEF DESCRI~TI~N OF nRAWIN(lS
Figs. 1 and 2 are partial plan views of two
major surfaces of a rubber sheet for use with turntable
in accordance with an embodiment of the present
invention.
Fig. 3 is a vertical cross-sectional view
ta~en on the line (V~-tV~ in Figs. 1 and 2.
Fig. 4 is an enlarged cross-sectional view
taken on the line (W~-(W) in Fig. 1.
Fig. 5 is a vertical cross-sectional view
showing an example of the shape of the edge portion of
the rubber sheet for use with a turntable in accordance
with the presen~ invention (that is, a vertical
cross-sectional view taken on ~he line (X~-(X) in Fig. 1).
Fig. 6 is a partial perspective view o-f an
example of an array of projections.
Figs. 7 and 8 are vertical cross-sectional
views showing an example of a projection with small
i
:~ 3 ~3~
- 15 -
recesses.
Fig. 9 is a partial perspective view of an
example of an array where projections o different shapes
are used in combination.
Fig. 10 is a partial, vertical cross-s~c~ional
view of the rubber sheet in accordance with the present
invention when being mounted on a turntable as well as a
disk record mounted on the ruhber sheet.
Figs. 11 to 13 are plan views of the rubber
sheet for turntable in accordance with the present
invention, wherein a plurali~y of insular arrays of
projections are provided.
Figs. 14 and 15 are plan views of two major
surfaces of the rubber sheet for turntable in accordance
with another embodiment of the present invention.
Fig. 16 is a vertical cross-sectional view
taken on the line (Y~-(Y~ in Figs. 14 and lS.
Figs. 17 and 18 are plan views of two major
surfaces of the rubber sheet in accordance with further
another embodiment of the present invention.
Fig. 19 is a vertical cross-sectional view
taken on the line (Z!-(z~ in Figs. 17 and 18.
Figs. 20a and 2~bJ 21a and 21b, 22a and 22b
and 23a and 23b are top views and cross-sectional views
of the conventional rubber sheets for turntable,
respectively.
Referring first to Figs. 1 through 4, the body
of a rubber sheet is generally designated as ~l) and a
center shaft hole is designated as ~2). A major surface of
the body (1! is provided with closely spaced-apart
projections (3~ in a plurality of concentric arrays (cf.
Figs. 1, 3, 4, this arrangement of projections is called
"Embodiment A"~. In the following, such a concentric
array of closely spaced-apart projections (3~ ~ill be
referred to as "array (4~ of projections". The number
of the arrays (4~ of projections is optional as long as
the body (1~ of the rubber sheet is held substantially
hori~on~ally on the turntable and may be typically 3 to
~ ~ ~35
- 16 -
]~. The arrays (4! of projections may be equally spaced
along the radial direction of the body (1~ of the rubher
sheet or as indicated in Figs. 1 and 3, a plurality of
blocks each comprising two or more close arrays (4) may
be provided rfor example, the two arrays (4b~ and (4c),
(4d~ ~nd (4e~,and (4f~ and (4g)]. It is to be understood
that the arrays t4! o projections may be disposed on
concentrically aligned ribs (5) as seen from Fig. 3.
Although in Embodiment A respective ones of
the projections (3~ in the arrays (4~ are usually flush
at their tops, they should not be limited thereto. For
example, when the major surface bearing the projections
(~ is to be in contact with the disk record, the
projections (3) are highest in the most inner array (4a)
(the nearest array with respect to the label section of
the disk record~ and lower gradually in the order of
the arrays (4b!, (4c!, (4d~, (4e), (4) and (4g~ so that
the disk record is substantially held by means of the
most inner array (4a! of projections and in no direct
contact with the remaining arrays (4b), (4c!~ (4d~, (4e),
(4f~ and (4g~ of projections other than the array (4a~.
In this embodiment, the disk record is maintained under
non-contacting relationship with the rubber sheet on its
periphery when the disk record is stationary. ~lowever,
when a pickup cartridge is in operating position for
playback of the disk record, the disk record comes into
contact with the rubber sheet due to the weight of the
cartridge w;th a minimum of contact area. This insures
an improvement in vibration inhibition.
The most outer array (4g~ is usually disposed
on an edge portion of the body (1) of the rubber sheet.
It is preferable that, as illustrated in a vertical
cross-section~l view of Fig. 5 (that is, an enlarged
cross-sectional view taken on the line (x!-(X! in Fig. 1~,
the edge portion of the body (1) is outwardly inclined
and the most outer array (4g~ of projections are disposed
on this inclined edge portion. According to this
embodiment, the edge portion of the body (l! of a
`~ ~B3~
relatively thin thickness offsets tension resistance of
the ruhber sheet and helps the close contact of the
rubber sheet with the turntable.
The projections (3) may take the various shapes
S as suggested previously in Embodiment A. F'referably,
the projections (3~ are ridge-shaped at least at the head
thereof. Fig. 4 depicts a typical example of the
projections (3~ which are of mountain profile with a
downwardly expanding skirt. For the projections (3) with
the ridge-shaped heads, it is also preferable that ridges
(3a~ extend along the radial direction of the body (1) of
the rubber sheet as seen from Fig 1. While the
projections (3~ in a particular array [e.g., (4d)] may
overlap with those in the adjacent array (4e~ along the
radial direction of the body (1~ of the rubber sheet, it
~ is desirable that the ridges (3a~ of the projections (3)
; in the particular array (4d~ be located in agreeement
with valleys ~6) bett~een the two adjacent projections (3)
in the other array (4e~ to avoid such overlapping
relationship as seen from Fig. 4. This alignment
provides better breathing behavior in a layer of air
confined between the rubber sheet and the turntable or
the disk record, thus completely shielding off the
external vibrations.
Another preferred shape of the projections (3)
in Embodiment A includes a pointed head. A partial
perspective view of Fig~ ~ [wherein the concentric array
(4~ of projections is re-aligned in a straight line]
depicts an example of such a shape of the projections
-30 (3~, typically a quadrangular pyramid. In a manner
:~ similar to the projections (3~ including the ridge-
; shaped heads, while the projections (3~ with the pointed
heads in the particular array re.g., (4d~] may overlap
with those in the adjacent array re.g., (4e~ along the
radial direction of the body (1~ o~ the rubber sheet,
it is also desirable that the pointed heads (3b) of the
projections (3! in the particular array (4d~ are located
in agreement with the valleys (6) between the ~t~o
' ,;
~ ~ ~3569
- 18 -
adjacent projections (3! along the radial direc~ion of
the body (1) of the rubber sheet to avoid such overlapping
relationship. Each of ~he foregoing projections (3) has
a single summi~ (3b) but may have two or more summits
(3a') which may be formed by providing the ridge of the
above-mentioned projection (3) having the r;dge-shaped
head with small recesses as shown in Eigs. 7 and 8. Fig.
7 is a vertical cross-sectional view showing one of the
projections (3~ with the ridge-shaped head having two or
more .summits (3a') along the radial direction of the body
(1~ of the rubber sheet and Fig. 8 is the equivalent
along the circumferential direction.
Furthermore, it is obvious that in Embodiment
A, the projections (3) with the ridge-shaped heads may be
aligned in combination with those with the pointed heads
or other different heads in the particular array (4).
An example of such combination is illustrated in a
perspective view of Fig. 9 r that is, a perspective view
wherein the concentric array (4) of projections is re-
aligned in a straight line]. In Fig. 9, the projections(3) with the pointed heads and those with the ridge-
: shaped heads [the latter is different from that in Fig. 4 in that the ridges (3a) are aligned along the
circumferential direction of the body (1~ of the rubber
sheet] are aligned alternatively with each other.
Preferably, as illustrated in Figs. 2 and 3,there are formed concentric grooves (7) in position to
correspond to the respective arrays (4) of projections,
on the opposite major surface of the rubber sheet having
the above illustrated projections (3! in accordance
~ith Embodiment A, so that the rubber sheet is uniform in
thickness as a whole. Each of the groo~es (7) may be
formed in correspondence with one of the individual
arrays (4) of ~he projections or a given number of
adjacent arrays (4) of projections as seen from Fig. 3
rfor example, one of the grooves (7) for each of the ribs
(5)]. With such an arrangement, the rubher sheet becomes
light in weight and the layer of air is also confined in
-
1 1 ~3~69
- 19 -
the grooves (7~, thus providing an improvement in
vibration absorption and tone quality. With the rubber
sheet having the arrays (4) of projections on the one
surface and the grooves (71 on the opposite surface, the
~one quality of reproduced sounds differs slightly
depending on which surface of the rubber sheet is to be
in contact with the turntable (or the disk record~.
Proper deter~ination as to which surface of the rubber
sheet is to be in contact with the turntable (or the disk
record~ results in providing agreeable reproduced sounds.
The turntable is usually provided with openings
in the intermediate portion between the center shaft and
the periphery thereof. It is thus favorable that, when
the surface having the grooves (7) formed therein is to
be in contact with the turntable, the most inner groove
(7) be kept away from the openings and a layer of air be
confined between at least the most inner groove (7) and
the turnta~le.
In the case where the one major surface with
the arrays (4l of projections is in contact with the
disk record and the other major surface with the grooves
(7~ in contact with the turntable in accordance with the
present invention, the preferred rubber sheet is that
wherein the projections (3~ are highest in the most inner
: 25 array (4a~ and lower gradually along the arrays (4b),
(4c!, (4dl, (4e~, (4f~ and (~g! and at least the most
inner groove (7) is kept away from the opening of the
turntable. Fig. 10 depicts the operating condition
where such a rubber sheet is mounted on the turntable
with the disk record resting on the rubber sheet. In
Fig. 1OJ the turntable is designated (8), the center
shaEt is designated (9!~ the openings of the turntable
are designated (10) and the dis~ record is designated
(11~. In the situation sho~n in Fig. 10, the rubber
sheet is in tight contact at its central portion
(corresponding to the lahel region of the disk record~
with the turntable (8~. ~ver the central portion of the
rubber sheet which is in tight contact with the turntable,
,
~ ~ ~35~9
- 2n -
there is involved the layer of air (l2) between the disk
record (ll! and the most inner array (4a) of the
projections on the rubber sheetO The air in the layer
(121 passes through the ga~s between the adjacen~
5 pToj ections in the array (4a) to thereby peTform the
breathing as stated abo~e during rep~oduction of the
disk record. On ~he other hand~ the most inner groove
(7a~ in ~he rubber sheet is s~aced from the opening (lO~
of the turntable (8) so ~hat a layer o air is
hermetically sealed within the groo~e ~7aj. ~ s
combination of the central portion of the
Tubber sheet ~hich is in tight contact with the turntable,
the layer ~12) of the moving air and the laye~ of the
heTmetically sealed air in the groove (7) p~ovides a
further improvement in ~ibration^damping prl~perties and
tone quality.
l~ile in the foregoin~ the concentric arTays
(4! of the closely aligned projeetions are adapted to
confine air with respect to the disk Teco~d or the
turntable, other arrangements of the projections
effecti~e to confine air appeaT available. For example~
as illustrated in plan views of Figs. 11 to 13, a
plurality of circular (including elliptic) arrays of
closely aligned projections (3), a plurality of
~5 polygonal (including a triangle and a quadrangle and so
on! arrays of closely aligned projections (3), a
plurality of fan-shaped arrays of closely aligned
projec~ions (3!, etc. (those will be referred to as
"insular arrays (13) or projections" hereinafter) may be
disposed outside the label section of the disk record.
In that case, air is conined by means of the individual
insular arrays ll3~ of projeotions ~o provide b~eath ng
beha~ior. In addition, the insular arrays (13) of
projections may be of the same dimension but a smaller one
(l3) may be interposed between two adj acent greater ones
(l3~ as seen from Fig. ll. Moreover, the differently
shaped insular arrays (13! of projections may be used
together as sho~ in Fig. 13. In ~his emb~diment, the
~ ~ ~35~9
- 21 -
concentric array (4~ of projections may be disposed at
the central portion or peripheral portion of the body
(1) of the rubber sheet together with the insular arrays
(13~ as seen from Eigs. 11 and 12.
Fig. 14 is a plan view of a major sur~ace of
the rubber sheet for turntable in accordance wi~h another
embodiment of the present invention, Fig. 15 is a plan
view of the other major surface of the rubber sheet of
Fig. 14 and Fig. 16 is a vertical cross-sectional view
taken on the line (Y)-(Y) in Pigs. 14 and 15. On the
one major surface there are provided closely aligned
projections (3) in a spiral array, as seen from Fig. 14
(this arrangement of projections is referred to as
"Embodiment B" hereinafter). In the following, such a
spiral array of the projections (3~ will be simply named
"array (14) of projections".
In Embodiment B, respective ones of the
projections (3~ in the array (14) may be all flush at
their tops or lower gradually in a direction toward the
periphery of the rubber sheet as in Embodiment A. Though
the projections (3! may take the various shapes as
discussed above, it is preferable that each of the
projections includes the ridge-shaped head or the
pointed head in the same manner as in Embodiment A. For
the former, it is preferable that the ridges be aligned
substantially in the radial direction of the body (1) of
the rubber sheet as viewed from Fig. 14. The projections
with the ridge-shaped head may be provided with small
recesses to form two or more summits as shown in Figs. 7
and 8. It is also apparent that the projections with the
ridge-shaped head may be used in combination with the
projections with the pointed head or the like as shown in
Fig. 9. In Embodiment B, preferably the edge portion of
the body (1~ of the rubber slleet is outwardly inclined in
a way similar to Embodiment A.
With regard to the other major surface of the
rubber sheet provided with the projections (3~ in
Embodiment B, it is also desirable that a portion
' ;
~ ~ ~3~
- 22 -
thereof corresponding to the array (1~) of proj~ctionsis made concave as depicted in Figs. 15 and lh ~as a
result, a convex rib (15~ is formed in the remaining
portion] to thereby make the thickness of the rubber
S sheet uniform as a whole. The edge portion of the other
major surface is usually provided with a flange portion
(16~ to confine air.
Fig. 17 is a plan view of a major surface of
the rubber shee~ for turntable in accordance with further
another embodiment of the present invention, Fig. 18 is
a plan view of the other major surface of the rubber
sheet of Fig. 17 and Fig. 19 is a vertical cross-
sectional view on the line (Z!-(z~ in Figs. 17 and 18.
Radial arrays of the projections ~re aligned on the one
major surface of the body ~1~ of the rubber sheet, as
seen from Fig. 17 (this arrangement of the projections
is referred to as "Fmbodiment C" hereinafter~. In the
following, the radial arrays of the closely aligned
projections will be simply named "array (17) of
projections".
In Embodiment C, respective ones of the
projections (3) in the arrays (17) may be all flush at
their tops or lower gradually in a direction to~rard the
periphery of the rubber sheet as in Embodiment A.
Though the projections (3) may take the various shapes
as discussed above, it is preferable that each of the
projections (3) includes the ridge-shaped head or the
pointed head in the same manner as in Embodiment A. The
projections with the ridge-shaped head may be provided
with small recesses to form two or more summits as sho~
from Figs. 7 and 8. It is also apparent that the
projections with the ridge-shaped head may be used in
combination with the projections with the pointed head or
the like as shown in Fig. 9. In Embodimen-t C, preferably
the edge portion of the body (l) of the rubber sheet is
outwardly inclined as in ~mbodiment A.-
With regard to the other.major sur~ace of therubber sheet provided with the projections (3~ in
I 3 ~;3~9
- 23 -
Embodiment C, it is also desirable that portions thereof
corresponding to ~he arrays (17~ of projections as shown
in Figs. 18 and 19 are made radially concave to form
radial concave parts ~18) in order to make the thickness
of the rubber sheet uniform as a whole.
Obviously, it is not necessarily re~uired to
align the projections (3) closely as in Embodiments A to
C. They may be aligned at any appropriate interval.
The rubber sheet for turntable in accordance
wi~h the present invention is free of any limitation as
to thickness. However, the rubber sheet usually has a
ma~imum thickness in the order of 2 to 8 mm. a minimum
thickness in ~he order of 0.1 to 3 mm. and ari average
thickness in the order of 0.1 to 6 mm. and more
particularly 0.5 to 2 mm.
The rubber sheet of the present inven~ion may
be made in a conventional manner. For example, the above
specified rubber composition is directly press-cured
within a mold of a given configuration. As an
alternative, a non-cured composition in the form of sheet
is prepared by calender molding or extrusion molding and
then subjected to press curing. Injection molding is
also available. It is also recommended that all of the
projections (3! be formed in the mold at one ~ime or
shaped by cutting after curing. Furthermore, the
projections (3~ may be made independently of the body (1)
of the rubber sheet and bonded to the body (l~ of the
rubber sheet with an appropriate adhesive or the like.
BEST MQDE FOR CARRYING OUT THE INVENTION
The rubber sheet for turntable in accordance
with the present inven~ion will now be described in
further detail by referring to Examples and Comparative
Examples.
Examples 1 to 4
Using the rubber compositions as enumerated in
Table 1, several rubber sheets for turntable ~ere
~ ~ 63~6~
- 24 -
manufactured.
Table l
Rubber Composition (in part)
_ .
Examples
1 2 3
Norsorex 150 NA (*1~ 250 250 250 250
~hite factice S (~2~ 225 20 26n 120
~ Sunthene 255 (*3~410 200 690 280
10 Dioctyl phthalate45 10 - -
FEF carbon 50 50 25 50
Zinc oxide 5 5 5 5
Stearic acid
Sumilizer MDP (*4) 2 2 2 2
15 Sulfur 2.5 2 ~ 2 2
Sunceller C~ (~5)10 8 12 9
*1: Polynorbornene ~Norsorex (resistered trademark~,
average molecular weight of not less than 2 x
106) extended with 150 parts of naphthenic oil
on the basis of 100 paTts of polynorbornene,
sold by Nippon Zeon Co., Ltd.
: *2: White factice made by Temma Sabu Kako Kabushiki
~Kaisha
*3: fflad~nark for Naphthenic oil made ~y Japan Sun~il Co.~ Ltd.
*4 Tradernark for 2,2'-Methylen~bis(4~ 1-6-tert.-butylphenol)
m~de by SumitomD Chemical Co., Ltd.
*5: Trademark for N-cyclohexy1-2-benzothiazyl sulfenamide made by
Sanshin Kagaku Kabushiki Kaisha.~
The rubber component was first scoured a~ about
: 60C. and kneaded with additional components through the
: :~ use of a Banbury mixer and a roller and shee~ed out to
giYe a sheet of about 2 to 3 mm. thick. The sheet was
: ~ . cut into a disk and cured by a press machine with a given
mold under a pressure of 150 kg./cm2 and at a temperature
of 155C. fbr-20 min.
The resultant rubber-sheets for turnt~ble
application were: con-Eiguration was one as sho~n in
'~
' ,: :
.
. ~
5 6 ~
- 25 -
Figs. 1 to 4 and 1~; diameter was 292 mm; maximum
thickness was 3.7 mm; minimum thickness was 1.9 mm;
height o~ the projections (3) in the most inner array
(4a~ was 0.5 mm. ~the height (Hl~ in Fig. 3] or 1.5 mm.
[the height (H2~ in Fig. 3]; length of the ridges of the
projections (3) was about 3 to 6.5 mm; depth of the
grooves (7) was 1 mm; and width of the grooves (7) (in
the radial directionl was about 30 mm. The individual
projections (3! were lower in height gradually toward
the periphery of the rubber sheet.
Various physical properties of the resultant
rubber sheets were measured with the results shown in
Table 2. r~easurements of impact resilience, tensile
strength and elongation were conducted according to JIS
K fi301-1969.
Table 2
.
Examples
Physical constants --------- - -
1 2 3 4
-
20 A hardness (degree~ 4 5 7 9
Impact resilience (~ 68 60 72 74
Tensile strength (kg./cm.) ~ 21 19 10
Elongation (~ 398 575 367 281
Specific gravity 0.977 0.98Z 1.0~30.987
Total area of the ridges of the projections
(3~ (S52 in total number) in each rubber sheet of
Exam~les 1 to 4 occupied about 1.45 ~ of the entire area
oE the one major surface of the rubber sheet (assuming
the width of the ridges was 0.25 mm.~. When a glass
sheet having the same ~imension as that o-E the rubber
sheet and a thickness oE 2 mm. (weight: about 300 g.)
was mounted on the one major surface of the rubber sheet
bearing the projections (3~, the rubber sheet was
substantially in contact with the glass sheet only at the
ridges of the projections (3) in the most inner array
(4a). In that case, the ratio of the contact area to the
entire area of the one major surface of the rubber sheet
1 ~ 6 ~
- 2h -
was ahout 0.1 ~. The preferred form of the rubber sheet
for turntable in accordance with the present invention
features minimizing the contact area in such a way.
The following tests were carried out on the
rubber sheets of Exam~les 1 to 4. For comparison, the
same tests were also carried out on four sorts of rubber
sheets affixed to players commercially available on the
market. The rubber sheets used herein were summarized
in Table 3.
rable 3
v Comparative Exam~les 1 2 3 4
Butyl SBR/NR Styrene- Butyl
~aterial rubber (*l~ butadiene rubber
rubber (*2)
A hardness (degree) 24 5n 57 36
Impact resilience (~ 19 - 33
Specific gravity 1~223 1.356 1.431 1.642
Halogenation No Yes Yes Yes
* Fig.20aFig.21a Fig.22a Fig.23a
Sha~e ( 3! Fig.20bFig.21b Fig.22b Fig.23b
*1: ~lixture of st~rene-butadiene rubber and natural
rubber
*2: Sheet body of butyl rubber covered with a mixture
of natural rubber and styrene-butadiene rubber
*3: Figs. 20a and 20b, 21a and 21b, 22a and 22b and 23a
and 23b are top and cross-sectional views of the
rubber sheets o Comparative Examples 1 to 4,
respectively. In these drawings thicknesses (hl~,
( 2!~ (h3~, (h4~, (hs)~ (h6~, (h7) and (h8~ of the
rubber sheets were as follows:
~hll: 4.2 mm.
(h2): 3.5mm.
(h3~: 5 mm.
(h4!: 4 mm.
(h5!: 3.5 mm.
(h6~: 2.5 mm.
(h7!: 5 mm.
- (h8l: 4.5 ~I.
3 :i 63~9
.
- - 27 -
Configurations were as follo~s:
Comparativ~ ~xample 1
Top surface: a circular recess of 0. 7 lTun . deep at
its center
; S Bottom surface: flat
COmpaTa t iY e Example 2
Top surface: a circular recess of 1.0 mm. deep at
its center and a concen~crically
- circular groove of 1. O mm. deep
Bottom surface: flat
Comparative Example 3
Top surface: a circular recess of 1.0 n~n. deep a~
its center
Bottom surface: flat
1~ Comparative Example 4
Top surface: three COnCentTically circular grooves
of 0. 5 mm. deep
Bottom surface: flat
It is noted tha t: the bottom surfaces of the
ru~ber sheets of Comparative Examples 1 to 4 were all
flat and in contac't wi~h the turntable. In carrying
out the following tests, the rubber sheets of
Comparative Exampl es 1 to 4 were mounted with their flat
bottom suTface in contact with the turntable.
2s (1! Tone quali~y cest
(i! Plav^back equipmen~t
Pre-main amplifier: AU-D307 (Sansui Electric Co.,
Ltd. )
Player: DP-40F (Nippon Columbia Co., Lt~. )
Cartridge: V-15 type 3 (Shure Brothers, Inc. )
401 (made by Mitsubishi Electric Corporation)
(ii) Listening roc~n
P~om of 66 m. in area (equipped with an air conditioner and
a ventilator)
Floor: Polyvinyl chloride-tiled (with mortared underlying layer)
C~iling: Fla~ noninfla~nable material (no sound~absorEJtion opening)
Inner walls: Ply~l
~.
3~B9
- 2~ -
(iii~ Test method
A panel of 4 trai~ed listeners A, B, C and D
was instructed to hear the following records and
score them on the following parameters. The
s rubber sheets of Examples 1 to 4 were set on the
turntable with the surface illustrated in Fig. 1
~one having the projections (3)] being in contact
with the record.
(~) Female vocal
Title of record: Valses, Canciones Y Tangos
~; (Nippon Phonogram Co., Ltd.)
Singer: ~inamaria Hidalgo
Accompaniment: ~lugo Videla (guitar) and
others
Program: Te Pido Que Lo Pienses
Parameters:
(a~ if reproduced sounds are near human
sounds
(b) if the treble region of soprano is not
distorted
(c) if accompanying guitar sounds are not
stronger than vocal sounds
(d~ if the impressions of presence are rich
(~) Concerto
Title of record: "Le Quattro Stagioni" ~8 by
Vivaldi (Nippon Phonogram Co., Ltd.)
Performer: Roberto ~lichelucci (violin) and
I Musici
Program: Concerto No. 1, E ~lajor RV 269
"Spring"
Parameters:
(a) if sounds of chords are vivid
(b) if the treble region is not distorted
(c) if the bass region is well-reproduced
~; 35 (d) i the impressions of presence are rich
(~) Flamenco gui~ar
Title of record: Manolo Sanl~car in Japan
(RVC Corporation)
35~9
- 2~ -
Performer: ~lanolo Sanl~car (guitar~, Isidro
(guitar~ and Jos~ 2~iguel (piano)
rrogram: Callej6n del Carmen
Parameters:
(a~if sounds of chords are we:Ll reproduced .
(b! if ~he treble region is not distorted
(c~ if beats of a guitar are well reproduced
(d~ if ~he impressions of presence are rich
The scores as to the above parameters were
10 determined according to the following fiv2-poin~ system.
5 polnts: Exceptionally good
4 points: Very good
3 points: Good
2 points: Ordinary
1 point : Poor
The sum of points as to each of the parameters
evaluated by each of the listeners multiplied by five
was regarded as overall evaluation by each of the
listeners ~if all of the parameters are evaluated as 5
points, overall evaluation would be full mar~s (lnO
points). Also, ~he average value of overall evaluations
by the four lis~eners was computed. Tables 4 to 9
indicate the results thereof.
.~
, ,s,,
~ :~ 63~9
- 30 -
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- 31 -
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35~9
- 34 -
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1., E (_) ~ ~ ~ 1.
¢ N C~
~ ~ ~ 1~1 LO L~ l 15~
~ ~ h ~1 ~ ~ ) o `O
~ ~ x a~ r~ U~
, ¢ I`n ~ Lr)
i~ ~
~ ~ ~ ~ O ~
~ O ~ ~ b~
1~ v~ o ~ ~ ~I td
v~ ~ ~ h t~ ,~ :~ h
~~ h o ~ u~ ~d
c~ ~ O ~ ~ ~d ~
a~ :~ ¢
o u 'C~ ~ ~ a)
.
1 1 S3!j~9
- 3f. -
( 2 ) Hohl ing test
Like~ise the tone quali1:y t~st, the listenersA, B, C and D were instructed to hear the three sorts of
records mentioned above and determine the presence or
S absence of ho~l ing on the basis of the follvwing
definition The pre-main amplifier was employed with
both treble and bass being located at "flat", while
volume pointed toward 11 o'clock.
Defini~ion of howling: Howling means all that
the tone quality of Teproduced sounds is
- deteriorated due to external vibrations
and repToduction of source sounds ~for
example, ~uman sounds of vocal~ is adversely
affected.
lS Howling was evaluated according to the 1~-
point system, wherein 10 points implied that no howling
~as observed and source sounds were reproduced as they
were. Decrease in points ;ndicated increase in howling
and 1 point indicated that howling was most severe and
reproduced sounds were most deteriorated. The results
are depicted in Table lO wherein "obverse" ~nd "reverse"
of the rubber shee~s of Examples 1 to 4 bear the
following mean;ngs.
Obverse: The surface as illustrated in Fig. 1
ri.e., one having ~he projections (3)
thereon] is regarded as a top surface
- (i.e., one in contact with the disk
record).
Re~erse: The surface as illustrated in Fig. 2
r i.e., one having the grooves (7! therein]
is regarded as a top surface.
Points in Table 10 show average values evaluated
by the four listeners (frac~ions were rounded off~.
~ .
:
-` `` J ~356~
- 37 -
C~ ~
~ ~ ,
.
~ ~ ~
o ~C
'
.
~ o X ~ ~ ~
:
~ ~ ,/ ~
o X
E~ ~ O` co co
X o~ o
O C~ ~ OD
~ C~ CO
~o ~~
`~ i ~ '
: ~ ~ ~ o
` .. . ::
, ` '
.
'
~, .
6 9
- 38 -
The results of the above detailed tone quality
test and howling test reveal that the rubber sheets of
the present invention (Examples 1 to 4~ were superior to
the conventional ruhber sheets (Cornparative Examples 1
to 4~. It is believed that the specific physical
properties and the specific configurations of the rubber
sheet of the present invention contributed to such
superiority. In other words, the rubber sheet of the
present invention is featured by very low hardness and
high impact resilience, i.e., a hardness of from not more
than 309 preferably not more than 20 in A hardness to
not less than 15, preferably not less than ~0 in F
hardness and an impact resilience of not less than 40 %,
preferably not less than 50 %. The rubber sheet of the
present invention offers the distinguished advantages of
closely sticking to the disk record or the turntable and
preventing a slip or resonance, as will be more clearly
understood from the results of slip tests and hoist
tests discussed below, and further insuring a minimum of
contact area by use of the projections with the specific
shapes and providing better breathing. As a result of
the combination of those characteristics, the rubber
sheet effectively prevents the tone quality of
reproduced sounds from deteriorating due to howling or
external vibrations and permits reproducing source sounds
as faithfully as they are. On the other hand, in the
case of the conventional rubber shee~s 9 the rubber sheet
of Comparative Example 1 was low in hardness, i.e. 24
in A hardness but low in impact resilience, i.e. 19 %,
and the rubber sheets of Comparative Examples 2 to 4
were high in hardness. The conventional rubber sheets,
therefore, neither met the criteria of ~he present
invention as to hardness and impact resilience nor did
they prevent the tone quality of reproduced sounds from
deteriorating due to howling or external vibrations.
(3! Slip test
AEter the rubber sheet was set on the ~urntable
oE a plaver (PL-380 made by Pioneer Electronic
~ ~3~
- 3g -
Corporation) together with a disk -record and was rotated
at a rate of ~3 1/3 r.p.m. with a stylus on the disk
record~ the disk record was urged to stop, by gripping
lightly the opposed radial edges of the disk record ~y
both hands, to therehy allow the operator to observe the
stopping movement of the turntable. The rubber sheet was
"qualified" when the turntable came to a stop immediately
after or within 1 second from interruption of rotating
the record and was "disqualified'l when it took more than
2 seconds for the turntable to come to a stop after
interruption of rotating the record. Table 11 shows the
results of this test.
Table 11
Rubber sheet Evaluation
- _
Example 1 Reverse "
.. ...
Example 3 Obverse
Obverse ''
Example 4 Reverse "
.. .. .. ~ .
Comparative Example 1 Disqualified
.. ~ ,.
" 3 "
" 4 ~e
In this test, the rubber sheets of Exa~ples 1 to
4 in accordance with the present invention were all
qualified, whereas even the sheet of Comparative Example
1 (non-halogenated conventional product~ which apparently
had the highest frictional resistance of all Comparative
- Examples 1 to 4 was disqualified.
(4! Lift ~est
This test was conducted to evaluate the
sticking properties of rubber shee~s.
The rubber sheet (of Comparative Example 3,
weight 340 g.~ to be lifted was placed on a de~k, with
:
3~9
- 40 -
its center shaft opening sealed with a cellophane tape,
and a rubber sheet to be tested was superimposed thereon
with the center shaft holes aligned. Then, with the test
rubber sheet gripped by thumb and index finger at its
center shat opening so as to stop up the opening, the
sheets as a unit were slid across the desk top beyond
the edge of the desk into suspension to see whether the
rubber sheet underlying the test rubber sheet would fall
off. Since the top surface of the rubber sheet of
Comparative Example 3 to be lifted was already halogenated,
the above test was carried out to study the influence of
halogenation, both in the case that the rubber sheet in
question was attached to the top surface of the rubber
sheet of Comparative Example 3, and in the case that the
same was attached to the bottom surface, i.e~ non-
halogenated surface, of the rubber sheet of Comparative
Example 3. The rubber sheet of Example 1 and the rubber
sheet of Comparative Example 1 ~which was deemed as
bearing the best sticking properties out of Comparative
Examples 1 to 4! were used as a rubber sheet in
question. The surface of the rubber sheet of Example 1 as
shown in Fig. 2 was held in contact with the rubber
sheet to be lifted and the flat surface (i.e. bottom
surface! of the rubber sheet of Comparative Example 1 in
contact with the rubber sheet to be lifted.
The results of lift test indicated that, while
the rubber sheet of Example 1 attracted tightlv the
rubber sheet to be lifted as a suc~er and lifted up it
and thus the rubber sheet did not fall, the rubher sheet
of Comparative Example l failed to a~tract or lift up
the rubber sheet to be lifted.
The above test made clear that the rubber sheet
of Example 1 was capable of lifting up the rubber sheet
of Comparative Example 3 with 3~0 g. weight. A further
test was carried out to determine what weight in gm. the
rubber sheet was capable of lifting up.
In other words, a plurality of the rubber sheet
of Comparative Example 3 were stacked with one on the
3~g
^ 41 -
other and adhered by use of a cellophane tape. Then,
the rubber sheet of Example 1 was mounted thereon and
subjected to the above procedure or liting.
As a result, it was revealed t~at the rubber
sheet of Example 1 was able to lift up up to ln sheets of
Comparative Example 3 (weight: 3.4 kg.~ en an attempt
was made to lift up 10 sheets of Comparative Example 3,
a break was developed at a portion of the rubber sheet of
Example 1 where was held by the operator and therefore
the test could be conducted no longer.
The foregoing slip and lift tests unveiled that
the rubber sheet in accordance with the present invention
exhibited a high friction resistance and excellent sticking
properties and served as a stabilizer, thus eliminating
the need for such stabilizer.
(5) Scratch test
This test was conducted on the rubber sheet of
Example 1 and the rubber sheet of Comparative Example 3
(which was subjected to halogenation treatment).
A cartridge portion of a player (SF-135 made by
Matsushita Electric Industrial Co., Ltd.) was provided
with a wèight and covered with a kraft paper so that a
load of about 3~ g. was applied to the rubber sheet on
the turntable with a contact area of about 2 cm. The
cartridge with the weight was located about 5 cm. inside
the periphery of the rubber sheet and the turntable was
rotated at a rate of ~5 r.p.m. The turntable was braked
to stop every 1 min. to find if any scratch was formed.
The above scratch test produced faint scratch
marks on the rubber sheet of Example 1 after about 30
minutes but those marks could be easily rubbed off wi~h a
finger. This was in contrast ~ith the rubber sheet of
Comparative Example 3, where the test produced in a short
time of 3 minu~es a large number of fine scratch marks,
though no~ very conspicuous, which could not be
obliterated with a finger.
The conventional rubber sheets are usually
halogenated to enhance surface hardness and reduce the
~ 3 ~3569
- 42 -
possibility of flaws developin~ on the sheet surface as
the rubber sheet of Comparative Example 3. As is evident
from the foregoing results, nevertheless no halogenation
treatmen~, the rubber sheet of the present invention is
5 less flawed than the conventional halogenated rubber
sheets. In addition~ fine flaws can be easily cleared
by finger as far as ~he rubber sheet of the present
invention is concerned.
~6) Dust attachment test
Ashes on the burned tip of 10 mm. long of a
cigarett were dropped on a sheet of pape~, crushed by
a finger and put on the test rubber sheet 2 cm. away
from its center. The rubber sheet was held up at a level
by both hands and then, one of the hands is left off
so that the rubbeT sheet hung down. Vsing the index
fingeT, the sheet was given 3 taps with a constant
pressure from the re~erse side of the sheet.
The ashes could be almost completely tapped
off in the case of the rubber sheets of Examples l to 4.
In the case of the rubber sheets of Compara~ive Examples
1 to 4, however 9 the ashes remained in the shape of a fan
with the original position of ashes as its apex. Mo~e
particula~ly, a substantial amount of the ashes remaired
on the non-halogenated rubber sheet of Comparati~e
Example 1.
It is appaTent from the foregoing tha~ a less
amount of dust was attached on the rubber sheet of ~he
present invention than that on the conventional rubber
sheets tComparative Examples 2 to 4~ which were subjected
to halogena~ion in order to lessen the possibility of
attachment of dust.
Examples 5 to 8
The same procedures as in Examples 1 to 4
except that the rubber compositions were changed to those
shown in Table 12 were repeated to produce rubber sheets
for turntable.
The phvsical constants of the resultant rubber
;
1 ~ 63~69
sheet~ r~ r: easured in the s;~me ~anner a~ in Example~ 1
to 4. The result~ are also dcpicted in Tabl~ 12.
Tabl e 12
Ex. 5Ex. 6Ex~ 7Ex. 8
.
Rubber Composition (in pa~ts~
Norsorex 80 7S 80 100
~ipol SBR 1712 (~1~ 20 - - -
Espl en e sn 5 ( * 2 1 - 2 5
~ipol IR 22tln (~3) - - 20
White factice S 420 3~n 320 210
Sunthene 55 56Q 450 440 320
Sunpar 110 (~ 4 ~ ~ ~ ~ 30
Sundex 790 (~5~ - ~ ~ 40
Dioc tvl phthalate - 80 - 50
FEF carbon 40 80 - 40
HAF carbon - - 40
~T carbon - - - 20
7inc oxide 5 5 5 5
Stearic acid
Sumilizer ~IDP
SulfuT 2.5 2.5 2.5 2 . ~
Sunceller C~ 10 10 10 9
Physical constants
A hardness (degree ! 5 7 5 8
Impact Tesilie~ce (~! 67 55 59 54
Tensile strength (kg.lcm2~ 2 5 9 8
Elongation (q~! lGl 155 257 402
Specific gravity 0.945 0.979 ~n.s5s 1.015
*l: Trademark for Styrene-butadiene ruhber made by NipFon Zeon Co., Ltd.
*2: Trademar~ for Ethylene-propylene-diene rubber made by Sumitomo
Chemical Co., Ltd.
~3 Trademark for Isoprene rubber made by Nippon Zeon Co., Ltd.
~4 Trademark for Paraff~nic oil made by Japan Sunoil Co., Ltd.
*5 Trademark for Aramatic oil made by Japan Sunoil Co,, Ltd.
The rub~er ~heetc of E~;aml-les 5 to 8 ~ermitte~
.
~ :~ 63~69
- 44 -
reproducing exc~llent tone quality sounds likewise the
rubber sheets of Examples 1 to 4.
Examples 9 to 10
The same procedures as in Examples l ~o 4
except that the rubber compositions were changed to those
shown in Table 13 were repea~ed to produce rubber sheets
for turntable. The physical constants of the resulting
rubber shee~s were measured in the same manner as in
Examples 1 to 4 and presented in Table 13.
Table 13
~x. ~ Ex. lD
Rubber Composition (in parts)
Norsorex 150 NA 250 250
D.O.G. factice F lD (*1~ 240 300
Sunthene 255 130 120
Dioctyl ph~halate 10
SRF carbon 40
MT carbon - 3~
~inc oxide 5 5
SteaTic acid
Ant;oxidant DDA (~2)
Suntig~t S (*3)
Sulfur 2 2
Sunceller CZ 8 6
Physical cons~ants
A hardness (degree! 18 23
Impact Tesilience (~ 71 73
Tensile strength (kg./cm. ! 21 16
Elongation (~) 283 293
Specific gravity 0.997 0.999
~1: Semitranslucen~ sulfur fac~ice made by D.O.G.
Deutsc~e Oelfabrick Ges. f. Chem. Erz. mbh ~ Co.
*7 Diphenylamine antioxidant made by Bayer A.G.
*3: Trad~E~k for Microcrystal~ne wax made by Seiko Xa~aku
Kabush~i Kaisha
,~, ,.
`J ~ ~356~
. .
- 45 -
In the case that a glass sheet of about 300 g.
weight was mounted on the respective rubber sheets of
Examples 9 to ln, contact area occupied about 0.01 ~ of
the entire area of a major surface of the ru.bber sheet.
~he following tests were conducted on the rubber
sheets of Examples 9 and 10.
(1~ Tone quality test
This test was conducted in the same manner as
in Examples l to 4 excep~ that the test record and
parameters were changed as follows: The results are
depicted in Tables 14 and 15 together with the results
obtained with the rubber sheets of Example 4 and
Comparative Examples 1 to 4.
Test record
Title of record: Bach: toccata and fugue? l?ower Biggs
at the Thomas Church (CBS Sony Inc.)
Performer: Power Biggs (organ)
Program: Toccata and fugue in D minor
Parameters
(a~ if peculiar sounds of a pipe organ were reproduced
(b~ if treble was clear
(c) if bass was solemn
(d~ if a melody was definitely separate from an
accompaniment
1 ~ 63S~9
- 46 -
~ ~ Ln U~
L~
~1 O
r) LO o
,; ¢ ~ o
~ u~ Lr) o
:: ~ ~
C t~ ~ ~ In Lr) o o~
~ ~ ~X a~ ~ Ln o
¢ Lt~ o
~ ~ r) o
'~ o
., o, ~ ~ O o
X P~ L~ o
~ ¢ LS~ LO Oo
`'. : ~ )
" ~ ~ 3 ~ c~
E; O
h ~ .--1
.~ ~ ~ O U ~ ~ C
o p~ J ~ a~
v~ O
~ ~ 63~9
- 47 -
a N ` -- N
~_ N ~ -- N
N N N ,~ ¦
N ~ ~ N ~
.~r-l ~ ~ O `O
. ~ ~ O ~C ~ N ) N 1~ ~ Ll )
E ~ ~ ~ ~ ~ a
~ 1 835~9
- 48 -
(2~ Howling test
The test was conducted in the same manner as
in Examples 1 to 4 except that the test record used in
the above ~one quality test was employed and the test
was carried out only in the case tha~ the rubber sheet
was mounted with its one major surface shown in Pig. 1
[provided with the projections (3~] in contact with the
record. The results are presented in Table lfi along
with the results obtained with the rubber sheets of
Example 4 and Comparative Examples 1 to 4.
Table 16
Fxample Howllng
9 10
4 10
,
Comparative Example 1 3
" 2 2
" 3 3
" 4 2
. The tone quality and howling tests as
illustrated above revealed that the rubber sheets of the
present inven~ion (Examples 9 and 10~ showed remarkable
advantages over the conventional rubber sheets
(Comparative Examples 1 to 4).
The rubber sheets of Examples 9 and 10 with A
hardnesses of 18 and 23, respectively, helped reproduce
well-sounded sounds as compared with the rubber sheet
of Example 4 with a lower hardness of 9 in A hardness.
(3) Slip test
This test was carried out in the same manner
as in Examples l to 4. The result was that the rubber
sheets of Examples 9 and 10 were both qualified.
(4) Lift test
This test was carried out on the rubber sheet
of Example 9 in ~he same manner as in Fxamples 1 to 4.
The result was that the rubber sheet of Example 9 was
3~69
- 49 -
able to lift up up to 10 sheets (weight: 3.4 kg.) of the
rubber sheet of Comparative Example 3.
(5) Scratch test
This test was also carried out on the rubber
sheet of Example 9 in the same manner as iYI Examples 1
to 4. The result was that a faint scratch was developed
after 30 min. but could be easily removed with once
rubbing by finger.
(6) ~ust attachment test
The same procedure as in Examples 1 to 4 was
effected. The result was ~hat less or no ashes remained
on the rubber sheets of Examples 9 and 10.
.,
Examples 11 and 12
The same procedures as in Examples 1 to 4
except that the rubber compositions were changed to those
shown in Table 17 were repeated to produce rubber sheets
for turntable.
The physical constants of the resulting rubber
sheets were measured in the same manner as in Examples
1 to 4. The results are presented in Table 18.
~ ;J B,3569
- 50 -
Table 17
Rubber composition (in parts~
Example
Components - --
11 12
Norsorex 150 NA 250 250
D.n.~. ~actice F ln 230 200
Sunthene 255 400
Sundex 790 - 1, noo
Rapeseed oil - 15
Dioctyl phthalateS0 35
FEF carbon 50
MT carbon - S0
,
Zinc oxide 5 5
: Stearic acid
,
: Antioxidant DDA 2 2
Suntight S
: Sulfur 2.5 2.5
Sance11er CZ 8 10
: ~ :
:
~ ~ ~3~69
- 51 -
U~ o~,
V~ ~o
~--I~ O
o
,~
,, ~4 ~, ~ ~
~ ~ ~ o
CO ~ ~o o
~ U~
X , ~
3~9
- 52 -
The following tests were effected on the rubber
sheets of Fxamples 11 and 12.
(1) Tone quali~y test
The test was carried out in the same manner as
in Examples l to 4 except that the test reccrd and
parameters were changed as follows: The results are
depicted in Tables 19 and 20 together with the results
obtained with the rubber sheets of Example 2 and
Comparative Examples 1 to 4.
Test record
Title of record: "1812 Overture" by Tchaikovsky
(Telarc Records1
Performer: The Cincinnati Symphony Orchestra
Conductor: Erich Kunzel
Parameters
(a~ if sounds of a cannon were well reproduced
(b) if treble was not distorted
(c1 if bass was well reproduced
(d~ if the impresslons of presence were sufficient
:
- 5 3
~ ~ n o
a~ c~ ~ ) Lr) o
~ m ~t ~ u, ~ ~
X ~ ~ Ln o
~ L~ o
o~ ~ C7 ~ U~ ~
~ ¦ E ~ m ~
~ ¢ ~ ~
L~ ~ L~
~ C~ ~ o o~
E m ~ ~ ~ , o o~
¢ L~ o
' ~ 0
C~ o
a~ ~ o ~ .,,
~ O ~ . ,D a~ ~ ~ ~
h v~ O .~ ,1 ::~ h
P~ ~ ~ o ~ ~ 0
5~ 0 ~d ~ ~ cc
~ ~ ~3~
- 54 -
a N N NN a
o~ X a~ c~ l L~
~ ~ I O
.~ o
h ~ ~ C~l C`l ~7~) L5~ ~
EP~ ~ c~ m
¢ ~ `t) O
O ~ ~c~ ~
E-~ h ~1 ~C~ Nt ~1 ~ iS)
E~ ~~:1 ~c~
¢ C~
~ C~
h ~1 C.) C~ O
E~ E~ p ~ cx~ ~ ~ ~t o Lt
¢ C~ ) O
O ~ .,1 ~
a) O rl ~ a~ ~ ~o
~ ~ ,~ ~ ~
t~ v~ O h h ~ ~ ~ h
1-~ ~ 1:: 0 ~ ~V t~ a)
1~ h ~ :~
O t~ O ~d
u~ 1 o
3~B~
55 -
~2~ Howling test
The test was conducted in the same manner as
Examples 1 to 4 except that the test record used in the
above tone quality test was employed and the test was
carried out only in the case that the rubber sheet was
moun~ed with its one major surface shown in Fig, 1
rprovided with the projections (3~ in contact with the
record. The results are shown in Table 21 along with
the results obtained with the rubber sheets of Example
2 and Comparative Examples 1 to 4.
Table 21
Example Howling
11 10
12 9
2 8
-
Comparative Example 1 4
" 2 3
" 3 3
" 4 2
~ _ ,. .
The tone quality and howling tests as
illustrated above revealed that the rubber sheets of
the present invention (Examples 11 and 12) showed
remarkable advantages over the conventional rubber sheets
(Comparative Examples 1 to 4~.
The rubber sheets of Examples 11 and 12 with C
hardness of 11 (F hardness of 73~ and F hardness of
31, respectively, further prevented howling and helped
reproduce sounds of superlow requencies as compared
with the rubber sheet of Example 2 with a higher hardness
of 5 in A hardness.
(3~ Slip test
This was carried out in the same manner as in
Examples 1 to 4. The result was that the rubber sheets
of Examples 11 and 12 were both qualified.
(4! Scratch test
This was carriecl out on the rubber sheet of
I ~ ~356~
- 5~ -
Example 11 in the same manner as in Examples 1 to 4.
The result was that a faint scratch was developed after
30 min. but could be easily removed with once rubbing by
finger.
(5) Dust attachment test
The same procedure as in Examples 1 ~o 4 was
effected. The result was that less or no ashes remained
on the rubber sheets of Examples 11 and 12.
Examples 13 to lS
The same procedures as in Examples 1 to 4
except that the rubber compositions were changed to those
shown in Table 22 were repeated to produce rubber sheets
for turntable.
The physical constants of the resulting rubber
sheets were measured in the same manner as in Examples 1
to 4. The results are presented in Table 23.
1 ~1 635~9
j,
Table 22
Rubber composition (in parts)
Example
Components - -
13 ~.4 15
- Nipol SBR 1712 13705 - -
~ Natural rubber - 100
:- Baypren-112 ~ - 100
D.O.G. ~actice F 10 200 250
D.O.G. factice NP 17 [~2~ - - 240
Sunthene 255 200 110 200
MT carbon 20 50 45
Zinc oxide 5 5
. 15 Magnesia ~ ~ 4
Stearic acid
Antioxidant DDA 2
Suntight S
: Sulfur 2 2 2
Sunceller CZ 4
Nocceler D~ 3~ - 2.7
" D (~4) - 0.7
~ " TT (*5~ _ 0.4
:~ " DT (*6~ - - 1.1
;~ 25 " TS (17~ _ _ lol
. .
*l Trademark for Chloropylene rubber m~de by Bayer A.G.
. *2: Semitranslucent sulfur factice made by D.O.G.
Deutsche ~elfabrick Ges. f. Chem. Erz. mbh ~
C o . .
*3:~ralem:rk for Curing accelerator made by Ouchi Chemical
Industry Co., Ltd.
*4: Trademark for Curing accelerator made by Ouchi Chemical
Industry Co., Ltd.
*5 Trademark for Curing ac oelerator made by Ouchi Chemical
Industry Co. J Ltd.
*6 Trademark for Curing accelerator made by Ouchi Chemical
Industry Co., Ltd.
~.
`.
s ~ g
- 5~ -
*7: Curing accelerator made by OUChi Chemical
- Industry Co., Ltd.
`:
``~ 3 5 6 9
- 59 -
.,,.,, o o~
C ~- o .
U) ~
C~
~0 ~ C11~ ~ N
~ ~ ~. LO C~
0,0 C`~
.
~1 ~4 U ~ `O
.,~ ~
~ a~ oo L~ ~
Q~
~--
C~
~J ~ ~ ~O `O
.,1
~a~ I I o~
a~ ~
h
h O ~ O
V) ~ ~ _
. ~ C~V) O~N~I
. .
` ~3~3~69
- 60 -
The following tests were effected on the rubber
sheets of Examples 13 to 15.
(1) Tone quality test
This tes~ was carried out in the same manner as
S in Examples l to 4. The results ara presented in Tables
24 to 26.
~ J ~3~9
- 61 -
n Ln U~
O N~
E~ a: LO ~ ~ Lr) Ln
'~: ~ o
a ~ ~ L~ u)
D ~ 11~ ~ Lf)
~-~ ¢ ~ o
~ ~ cl~
t~ t~ ~ cr~ 10
:~ ~ ~r ~ D
¢ Ir) Ir) LO 1~) O
j~ ~ ~:
E~ v) ~ ~ ~ ~ ~ ~
~ u~ t.) ~I c~ t~
h tD 1~ ~ ::~ ~
t~ ~ tC O,D E~ c~ ~ ~I>
h ~ ~
:~ cC
. a~ s ~ ~ ~>
Z C:l C C~ O
~ ~ ~3s6g
- 62 - I
U~ ~ ~ t)
~:4 ~ Lf~ o ~
x m In Lr, ~ ~ o
¢ ~ ~
~ ~ o
et ~ L~ U~ L~ '.
h~ Cb ~ O ~ ~
¢ Ln LO U~ Lr) ~
~; ~ U) L~ ~ LO O`
r~7 ~ L~ ) O ~O
: ~ ~ ~ m ~ ~ ~
¢ L~ Lt) O~
~ ~a~ ~
a~ ~ o ~ .,~ ~
~rl ~ a) ~ ~o
~ ~ ~1 ~ ~d
h v~ ~ h ~ ~: r~
s~ o ~ a3 ~d
h t~ ~
~ ~ ~ ¢
O ~ O ~ ~ ~ ~
U') ~ X ~ O
~ ~J8~
- ~3 -
n o
~n C~
~ ~ ~ Lr) L~
,~ o~ ~
~ ~ ~ Lr3 ~
¢ u~ LO m
~ Lr) ~ Lr~
h
~d ~t ~ ~ C~
v .~ a~ . ~
.n~ o ~ F~ ~ LS)
E- ~ ¢ L~ Lr) Lr) Lr) O
C~ L~ O
. ~_ O~
~; ~, D ~ D D D
V~
h ~ ~ O
~) 4~ 0 r-l ~ ~1 a.)
E~ o ~ ~ ~)
u~~ ~ O h U r~ ) tl~
h ~ ~h h t~ ~: ~1 ~ h
t~ ~) hO ~-\ ul ~ a~ t~
P., ~ O ~ ~--.rl V) h ~ ~
~ a) ~ ~ ¢
o u~ o a~ t~) h ~ C~
u~ O
`:
1 ~ 835B9
- 64 -
(2) Howling test
The test was conducted in the same manner as
in Examples 1 to 4 excep~ that the test was carri~d out
only in the case that the rubber sheet was mounted with
- S its one major surface shown Fig. 1 tprovided with the
projections (3~] in contact with the record. The results
thereof are presented in Table 27.
Table 27
Example
Record --
13 14 15
Female vocal 8 8 8
Concerto 9 8 8
Flamenco guitar 9 8 8
The tone quality and howling tests as
illustrated above revealed that the rubber sheets of
the present invention (Examples 13 to 15) showed
remarkable advantages over the conventional rubber sheets
~0 (Comparative Examples 1 to 4, see Tables 5, 7, 9 and 10).
(3~ Slip test
This test was carried out in the same manner
as in Examples 1 to 4. The result was that all of the
rubber sheets of Examples 13 to 15 were qualified.
(4~ Lift test
This test was carried out on the rubber
sheet of Example 13 in the same manner as in Examples 1
to 4. The result was tha~ the rubber sheet of Example 13
was able to lift up to 6 sheets (weight: 2.0 kg.) of the
rubber sheet of Comparative Example 3.
(5~ Scratch test
This was also carried out on the rubber sheet
of Example 13 in the same manner as in Examples 1 to 4.
The result was that a faint scratch was developed after
30 min, but could be easily removed with once rubbing by
finger.
(~) Dust attachment test
The same procedure as in Examples 1 to 4 was
.,
~ 1 ~3~
- 65 -
effected. The result was that less or no ashes remained
on the rubber sheets of Examples 13 to 15.
Examples 16 to 19
The same procedures as in Examples 1 to 4
except that the rubber compositions were changed to those
shown in Table 28 were repeated to produce rubber sheets
for turn~able.
The physical constants of the resulting rubber
sheets were measured in the same manner as in Examples l
to ~. The results are presented in Table 29.
~ ~ ~35~g
- 66 -
1able 2B
Rubber composition (in parts)
Example
Components - . _
- lfi 17 18 l9
Nipol SBR 1712 137. 5 - - -
Nipol IR 2200 - 100
Nordel 1040 (*1~ - - 100
Millathane 76 (*2~ lû0
D.O.G. factice F 10 230 200 250
D.O.G~ factice NP 17 - - - 200
. D.O.G. faccice DS SOFT (~3) - 15 - -
. Sunthene 255 200 15 20û 250
Sunp ar 110 - 7 Q
Thiokol TP-95 (*4) - - - 10
SRF carbon - 5
MT carbon 60 - 50
Light calcium carbonate - - - 10
2Q Zinc oxide 5 5 5
- Zinc stearate - - - 0. 5
Stearic acid
Antioxidant DI)A 2
' Suntigrht S
Sulfur 2 2.2 2.5 1.5
v I Sunceller CZ 4 2
Nocceler D~ - - - 3
~, " TT - - 1. 2
M (*5) - - 2 2
" TRA (*6) _ 102
~: Thioko.l ZC 4 56 ( * 7 ~ - - - 1
*1: Tr=~em3rk for Eth~lene-proF~lene-diene c~polym~r made by E. I.
Du Pont de Nemours & Co.
*2 Trademark for Urethane rubber made by Technical Sales &
Engineering Inc.
~3: Soft semitranslucent sulfur factice made b)r
D.Q.G. Deutsche Oelfabrick Ges. f. Chem. Er~.
,~
1 1 63~9
-
- 67 -
: mbh ~ Co.
~4: Trademark for Plasticizer made by Thiokol Corp.
: ~5: Curing accelerator made by Ouchi Chemical
Industry Co.g L~d.
~6: Curing accelera~or made by Ouchi Chemical
Industry Co., Ltd.
*7: Curing accellerator made by Thiokol Corp.
::
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:
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~"
:
:
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;. :
,~ .
. :
- ~ ~
. - -
:, ~ : : ,
.: :
'- :
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.
: ~:
~ .
'''
. ' .
i 1 ~3~9
`'. :
- 68 -
, V~ ~ C~
CJ td O O~ O~ O
~_
~ ~ ~ C~ ~ c~l
O
rC
a~
'J )::: ~ ~ ~O ~ C`J
v~ C`l
~:: h ~0
Cl~ ~ ~
o~
,9 ~ C~ ~ C~l
~ ~ C~ Ll~ 1 ~)
': Cl~
C~ ~ `O ~3 LO C\l
a~ ~
~'~ ~:) ~I
Cl~ U~
h ~ 0 0 `O ';t
: ~ c cl
, ~ ~ ~ 1~ 0 C~
., ~Ll ~
~ ;1 63569
- 69 -
Likewise the rubber sheets of Examples 13 to
15, the rubber sheets of Examples 16 to 19 permitted
reproducing excellent tone quality sounds.
