FIELD OF THE INVENTION
[0001] This invention relates to an insulating structure of a switch comprising a molded
article of an organic composite material, which structure withstands impact of an
increase in pressure inside the switch on breaking the circuit. More particularly,
it relates to molded insulating structures constituting a switch, including a housing
and inside parts, which do not suffer from deformation, a crack or a break even when
exposed to an impact of an increase in pressure inside the switch due to explosive
expansion of decomposition gas generated from the housing and the inside parts on
cutting off the current.
BACKGROUND OF THE INVENTION
[0002] Fig. 1 is a schematic perspective view of a general circuit-breaker. In the figure,
numerals 1, 2, and 5 are a cover, a base, and a handle, respectively. Fig. 2 is a
schematic view of the circuit-breaker shown in Fig. 1 with its cover removed, in which
cross-bar 3, trip bar 4, handle 5, contact point 6 of a movable contactor, and contact
point 7 of a fixed contactor as shown in Fig. 3 to 6 are provided. Cross-bar 3, trip
bar 4, and handle 5 are generally made of an insulating structure molded of an organic
composite material.
[0003] In a switch such as a circuit-breaker, when movable contactor point 6 and fixed contactor
point 7 are disconnected with electricity applied, an arc is generated between them.
On account of the arc, the organic material around the contact point and inside the
switch thermally decomposes to generate gas to steeply rise the pressure inside the
switch. The increased pressure gives an impact to the housing of the switch, i.e.,
cover 1 and base 2, as well as the inside parts, i.e., handle 5, cross-bar 3, and
trip bar 4.
[0004] Insulating structures in conventional circuit-breakers have been made of phenolic
resins or polyester resins. Those made of phenolic resins usually comprise 50 wt%
of a phenolic resin, 30 wt% of woodmeal, 15 wt% of an inorganic filler, and 5 wt%
of a pigment and other additives. Insulating structures for a switch, for example,
a housing comprising a polyester resin are disclosed in JP-A-5-202277. (The term "JP-A"
herein used means an unexamined published Japanese patent application.) In addition,
a housing comprising 25 wt% of an unsaturated polyester resin, 60 wt% of calcium carbonate,
and 15 wt% of glass fiber; a handle comprising 70 wt% of polybutylene terephthalate
and 30 wt% of glass fiber; a cross-bar comprising 55 wt% of a phenolic resin and 45
wt% of glass fiber; and a trip bar comprising 70 wt% of polybutylene terephthalate
and 30 wt% of glass fiber are known.
[0005] In cases where a switch, such as a circuit-breaker, is reduced in size or increased
in capacity to be cut off, the above-mentioned pressure rise inside the switch due
to the gas of the thermally decomposed organic material is more steep than generally
received. In high capacity cut-off in particular, the arc gas is nearly explosive.
Therefore, the aforesaid conventional materials are insufficient for preventing deformation,
cracks or breaks of the housing and inside parts after cut-off.
[0006] Furthermore, in the PATENT ABSTRACTS OF JAPAN, vol. 18, no. 528 (C-1258), October
6, 1994 & JP-A-06 184398 there is disclosed a composition suited for use as an automotive
relay box, which comprises nylon 6, nylon 66 and an ethylene/α-olefin copolymer. However,
the resin composition of this document also comprises modified aromatic poly(phenylene
ether) as a major resin component and therefore will have a reduced arc extinguishing
property.
SUMMARY OF THE INVENTION
[0007] The present invention has been achieved to solve the above-described problem of conventional
techniques by incorporating an impact-absorbing component into a molding material
for insulating parts composing a switch. Accordingly, an object of the present invention
is to provide an insulating structure of a switch, i.e., a housing or an inside part,
comprising a molded article of an organic/inorganic composite material, which structure
withstands a rise of pressure inside the switch due to decomposition gas generated
from the organic material of the structure at the time of high capacity cut-off of
the switch without undergoing deformation, cracking or breakage.
[0008] The insulating structure of a switch according to the present invention is a molded
article of an organic composite material comprising nylon 6, nylon 66, and nylon MXD
6 as matrix resins, and further an ethylene/α-olefin copolymer as an impact-absorbing
component, and a reinforcement (hereafter referred to as the first embodiment).
[0009] The another insulating structure of a switch according to the present invention is
a molded article of an organic composite material comprising nylon 6 and nylon 66
as matrix resins, and further an ionomer of polyolefin as an impact-absorbing component,
and a reinforcement (hereafter referred to as the second embodiment).
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] Fig. 1 is a schematic perspective view showing the appearance of a circuit-breaker.
[0011] Fig. 2 is schematic perspective view of the circuit-breaker with a cover removed.
[0012] Fig. 3 is a perspective view of a contact point of a movable contactor and a contact
point of a fixed contactor.
[0013] Fig. 4 is a perspective view of a handle.
[0014] Fig. 5 is a perspective view of a cross-bar.
[0015] Fig. 6 is a perspective view of a trip bar.
[0016] Fig. 7 is a perspective view of a cover.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The organic composite material for the insulating structures of the switch of the
first embodiment comprises 35 to 39 wt% of nylon 6, 8 to 12 wt% of nylon 66, and 1
to 3 wt% of nylon MXD 6 as matrix resins, 7 to 9 wt% of an ethylene/α-olefin copolymer
as an impact-absorbing component, and 40 to 45 wt% of a reinforcement. The composition
ratio is based on the total weight of the organic composite material. The organic
composite material having the above composition can be injection-molded to obtain
each insulating structure.
[0018] The feature of the above organic composite material resides in that the combination
of nylon 6 and nylon 66 has no aromatic ring and improves performance in arc extinguishing.
Further, the combined use of nylon 6 and nylon 66 delays crystallization of the matrix,
which favors gloss of the molded article. In further combining nylon MXD 6 with the
combination of nylon 6 and nylon 66, it is preferable to fit a mold for injection
molding with a quenching means so that the mold may be cooled simultaneously with
injection of the resin to lower the mold temperature in contact with the surface of
the insulating structure. By doing this, nylon MXD 6 is rendered less crystallizable,
resulting in further improvement in gloss of the molded article. Further, since the
matrix resins are thermoplastic, it is possible to reduce the curing time in molding
and to obtain a molded article having a complicated shape even with a thin wall.
[0019] The term "nylon" as used herein means an ordinary synthetic linear polyamide resin.
The designation "nylon
mn" as used herein denotes a polycondensate of a diamine having
m carbon atoms (NH
2(CH
2)
mNH
2) and a dibasic acid having
n carbon atoms (HOOC(CH
2)
n-2COOH). The designation "nylon
n" as used herein denotes a polymer of an ω-amino acid having
n carbon atoms (H
2N(CH
2)
n-1COOH) or a lactam having
n carbon atoms.
[0020] The organic composite material of the first embodiment contains, as an impact-absorbing
component, an ethylene/α-olefin copolymer which is hardly hygroscopic, whereby the
resulting molded article obtained therefrom has reduced hygroscopicity, improved impact
resistance, and improved machinability in, for example, tapping and improved impact
fatigue resistance.
[0021] The ethylene/α-olefin copolymer used in the first embodiment preferably contains
up to 3 mol% of α-olefin as a comonomer component, examples of which includes propylene
and methylpentene.
[0022] The preferred composition ratio of the above-described components was decided based
on the following reasons as a result of tests on various combinations.
[0023] If the ratio of nylon 66 in the organic composite material exceeds 12 wt%, the appearance
of the resulting molded article tends to be deteriorated. If it is less than 8 wt%,
the molded article tends to have reduced heat resistance.
[0024] When molded at a mold temperature lower than 120°C, nylon MXD 6 in the specific organic
composite material of the present invention becomes amorphous to provide satisfactory
outer appearance. If the ratio of nylon MXD 6 is less than 1 wt%, the appearance tends
to be deteriorated. If it exceeds 3 wt%, the aromatic ring in nylon MXD 6 tends to
adversely affect the insulation performance after cut-off.
[0025] If the ratio of the ethylene/α-olefin copolymer exceeds 9 wt%, or if the ratio of
the reinforcement is less than 40 wt%, the resulting molded article tends to have
insufficient rigidity. If the ethylene/α-olefin copolymer is less than 7 wt%, or if
the one or more reinforcements exceeds 45 wt%, the resulting molded article tends
to have insufficient impact resistance.
[0026] The organic composite material for the insulating structures of the switch of the
second embodiment comprises 25 to 27 wt%, particularly 26 wt% of nylon 6 and 23 to
25 wt%, particularly 24 wt% of nylon 66 as matrix resins, 6 to 8 wt%, particularly
7 wt% of an ionomer of polyolefin as an impact-absorbing component, and 42 to 44 wt%,
particularly 43 wt% of a reinforcement.
[0027] The feature of the above organic composite material resides in that the matrix resin
is a thermoplastic resin comprising nylon 6 and nylon 66 so that the curing time in
molding may be shortened and a molded article of complicated shape can be obtained
even with a small wall thickness. Further, the ionomer of a polyolefin copolymer compounded
as an impact-absorbing component serves as an elastomeric component to improve impact
resistance and arc extinguishing properties.
[0028] Since the composite material contains an ionomer of polyolefin which is hardly hygroscopic
and a reinforcement, the insulating structures obtained therefrom have reduced hygroscopicity.
Further, the incorporation of an ionomer of poleolefin improves physical machinability,
for example, in tapping and it also brings about an improvement in impact fatigue
resistance.
[0029] The ionomer of polyolefin used in the second embodiment is not particularly limited,
and it may be a conventional thermoplastic resin having polyolefin chains crosslinked
by ionic bond. Preferred examples are modified or unmodified EPDM (ethylene/propylene/diene/monomer)
rubbers, and terpolymers of ethylene, methacrylic acid-zinc neutralization product
and an acrylic acid ester.
[0030] The reinforcement to be used in both the first and second embodiments of the present
invention will be illustrated below. The insulating structure of a switch according
to the present invention is a molded article of an organic composite material containing
resins, an impact-absorbing component, and at least one kind of a reinforcement. The
reinforcement is used for improvements of strength against pressure, rigidity, and
arc extinguishing properties. The reinforcement comprises at least one kind selected
from the group consisting of glass fiber, inorganic minerals, and ceramic fiber.
[0031] Substances present as impurity in the reinforcement of an insulating structure of
a switch are decomposed by the high temperature of the arc at the time of high capacity
current cut-off into molecular gas. Among such impurities a compound of a metal of
the Group 1A of the Periodic Table (e.g., Li, Na, K, Rb, Cs or Fr) is decomposed into
conducting ion gas by the heat of the arc. The resultant conducting ion interferes
with arc extinguishing and reduces the arc extinguishing performance of a switch.
In addition, the conducting ion is chemically bonded to other ion gas generated therearound
and thus deposited on the inside of the switch. Having conductivity, the deposit has
been a cause of deterioration of insulating performance after cut-off.
[0032] As a result of experimentation, where the content of a metallic compound of a metal
of the Group 1A of the Periodic Table in the form of an oxide (e.g., Na
2O, K
2O or Li
2O) in the reinforcement exceeds 1 wt%, the arc extinguishing performance is considerably
reduced. A range of the metallic compound content in the reinforcement which will
not give influences on the arc extinguishing performance is not more than 0.6 wt%,
preferably not more than 0.15 wt%. Removal of the Group 1A metal oxides involves an
increase in cost for purification of the reinforcement. A preferred metal oxide content
which does not greatly impair the arc extinguishing performance and the insulating
performance without causing an increase of purification cost ranges from 0.6 to 0.1
wt% based on the total weight of the reinforcement.
[0033] Specific examples of the inorganic minerals to be combined as a reinforcement include
calcium carbonate, clay, talc, mica, barium peroxide, aluminum oxide, zircon, cordierite,
murite, wollastonite, muscovite, magnesium carbonate, dolomite, magnesium sulfate,
aluminum sulfate, potassium sulfate, barium sulfate, zinc fluoride, and magnesium
fluoride. They are effective to improve heat distortion resistance and dimensional
stability.
[0034] Calcium carbonate, talc, wollastonite, barium peroxide, aluminum oxide, magnesium
carbonate, magnesium sulfate, aluminum sulfate, potassium sulfate, barium sulfate,
zinc fluoride, and magnesium fluoride are preferred reinforcements; for they satisfy
the requirement of the total content of the Group 1A metal compounds.
[0035] From the viewpoint of strength against pressure, calcium carbonate is preferably
treated with a surface modifier, such as an aliphatic modifier, e.g., stearic acid,
so as to have improved dispersibility in the matrix resin.
[0036] The terminology "ceramic fiber" as used herein means fibrous materials made of ceramics.
The ceramic fiber is not particularly limited as long as the condition described above
with respect to the total content of metallic compounds of the Group IA metal of the
Periodic Table is satisfied. Specific examples of the ceramic fiber include aluminum
silicate fiber, aluminum borate whisker, and alumina whisker. They are favorable from
the standpoint of improvement in arc extinguishing properties and strength against
pressure.
[0037] The ceramic fiber preferably has a diameter of 1 to 10 µm and an aspect ratio of
not smaller than 10 from the viewpoint of strength against pressure.
[0038] The reinforcements to be used in the molded insulating structures are preferably
fibrous ones for enhancing the strength and toughness of the molded article. Glass
fiber is particularly suitable for the molded insulating structures of the present
invention for the following reason. Glass fiber is compatible with the matrix resins,
nylon 6 and nylon 66, and is uniformly distributed throughout the molding material
to provide a molded article free from local brittleness and having satisfactory impact
resistance. Since glass itself is heat-resistant material, the resulting molded insulating
structure has satisfactory resistance to heat and explosive gas pressure of the arc.
[0039] The terminology "glass fiber" as used herein means fibrous materials made of glass.
The glass fiber is not particularly limited as long as the condition hereinafter described
above with respect to the total content of metallic compounds of the Group IA metals
of the Periodic Table is satisfied. Examples of glass material include E glass, S
glass, D glass, T glass, and silica glass.
[0040] Fibrous glass products include long fibers, short fibers, and glass wool. Short fibers
are preferred as a reinforcement for thermoplastic resins. Glass fiber as a reinforcement
for thermosetting resins is not particularly restricted.
[0041] From the standpoint of strength against pressure, the glass fiber preferably has
a diameter of 6 to 13 µm and an aspect ratio of not smaller than 10. The glass fiber
is preferably treated with a silane coupling agent, and the like for ensuring strength
against pressure.
[0042] The above-mentioned reinforcements may be used either individually or as a combination
of two or more thereof. Combinations of two or more kinds of reinforcements include
a combination of glass fiber and an inorganic mineral or ceramic fiber; a combination
of an inorganic mineral and ceramic fiber; a combination of two or more kinds of glass
fiber; a combination of two or more kinds of inorganic minerals; a combination of
two or more kinds of ceramic fiber; and a combination of glass fiber, an inorganic
mineral, and ceramic fiber. While not particularly limiting, the combination of glass
fiber and an inorganic mineral has an advantage of low cost of raw materials.
[0043] The insulating parts of a switch according to the present invention, such as a housing,
a cross-bar, a handle, and a trip bar, can easily be prepared by molding the above-described
organic composite material by injection molding, and the like. The resulting housing
can be prevented from being cracked, deformed or broken due to an explosive increase
of the inner pressure at the time of high capacity cut-off, and the impact resistance
of the switch at the time of cut-off can be improved and the insulating properties
of each of these structures can be retained after the cut-off.
[0044] The present invention is further explained below with reference to the following
Examples. However, the present invention should not be construed as being limited
thereto.
EXAMPLE 1
[0045] A cover, a part of a housing, as shown in Fig.1 was prepared using an organic composite
material comprising nylon 6, nylon 66, and nylon MXD 6 as matrix resins; an ethylene/α-olefin
copolymer as an impact-absorbing component; and glass fiber, ceramic fiber, and wollastonite
as reinforcements. For comparison, a cover was prepared using an unsaturated polyester
resin as a matrix resin. The resulting cover was assembled into a circuit-breaker
and tested by a cut-off test.
Cut-off Test:
[0046] An excessive three-phase current of 460 V/30 kA was passed with the circuit closed.
The movable contactor was moved to break the contact and generate an arc current.
A circuit-breaker whose housing and inside parts suffered from no breakage or cracks
was regarded to be acceptable. The results obtained are shown in Table 1 below.
[0047] As is shown in Table 1, the comparative sample 1 using the conventional product suffered
from damage, whereas no cracking or damage was observed with the samples of the present
invention. While the samples tested were molded articles of the first embodiment,
those obtained from the organic composition materials of the second embodiment were
also satisfactory, being free from cracking or damage.
EXAMPLE 2
[0048] A handle shown in Fig. 3, a cross-bar shown in Fig. 4, and a trip bar shown in Fig.
5 were prepared by molding the organic composite material of the second embodiment.
A combination of nylon 6 and nylon 66 was used as a matrix resin, an ionomer of a
polyolefin copolymer was used as an impact-absorbing component, and glass fiber, ceramic
fiber and wollastonite were used as reinforcement(s).
[0049] For comparison, a handle and a trip bar were prepared using a polybutylene terephthalate
as a matrix resin (comparative samples 2 and 4), and a cross-bar was prepared using
a phonolic resin as a matrix resin (comparative sample 3).
1. An insulating structure for a switch wherein the insulating structure is a molded
article of an organic composite material which comprises 35 to 39 wt% of nylon 6,
8 to 12 wt% of nylon 66, 1 to 3 wt% of nylon MXD 6, 7 to 9 wt% of an ethylene/α-olefin
copolymer, and 40 to 45 wt% of a reinforcement.
2. The insulating structure for a switch as in claim 1, wherein said reinforcement contains
not more than 0.6 wt% of an oxide of a metal of the Group 1A of the Periodic Table
based on the weight of the reinforcement.
3. The insulating structure for a switch as in claim 1, wherein said reinforcement comprises
glass fiber.
4. The insulating structure for a switch as in claim 1, wherein said molded insulating
structure is a housing of a switch.
5. The insulating structure for a switch as in claim 1, wherein said molded insulating
structure is a handle, a cross-bar or a trip bar which is a part in the inside of
a switch.
6. An insulating structure for a switch wherein the insulating structure is a molded
article of an organic composite material which comprises 25-27 wt% of nylon 6, 23-25
wt% of nylon 66, 6-8 wt% of an ionomer of polyolefin, and 42-44wt% of a reinforcement.
7. The insulating structure for a switch as in claim 6, wherein said organic composite
material comprises 26 wt% of nylon 6, 24 wt% of nylon 66, 7 wt% of an ionomer of a
polyolefin, and 43 wt% of reinforcement.
8. The insulating structure for a switch as in claim 7, wherein said reinforcement contains
not more than 0.6 wt% of an oxide of a metal of the Group 1A of the Periodic Table
based on the weight of the reinforcement.
9. The insulating structure for a switch as in claim 7, wherein said reinforcement comprises
glass fiber.
10. The insulating structure for a switch as in claim 7, wherein said molded insulating
structure is a housing of a switch.
11. The insulating structure for a switch as in claim 7, wherein said molded insulating
structure is a handle, a cross-bar or a trip bar which is a part in the inside of
a switch.
1. Eine isolierende Struktur für einen Schalter, wobei die isolierende Struktur ein Formartikel
aus einem organischen Verbundstoffmaterial ist, welches 35 bis 39 Gew.-% Nylon 6,
8 bis 12 Gew.-% Nylon 66, 1 bis 3 Gew.-% Nylon MXD 6, 7 bis 9 Gew.-% eines Ethylen/α-Olefin-Copolymers
und 40 bis 45 Gew.-% eines Verstärkungsmaterials umfaßt.
2. Die isolierende Struktur für einen Schalter wie in Anspruch 1, wobei das Verstärkungsmaterial
nicht mehr als 0,6 Gew.-% eines Oxids eines Metalls aus der Gruppe 1A des Periodensystems
bezogen auf das Gewicht des Verstärkungsmaterials umfaßt.
3. Die isolierende Struktur für einen Schalter wie in Anspruch 1, wobei das Verstärkungsmaterial
Glasfasern umfaßt.
4. Die isolierende Struktur für einen Schalter wie in Anspruch 1, wobei die geformte
isolierende Struktur ein Gehäuse eines Schalters ist.
5. Die isolierende Struktur für einen Schalter wie in Anspruch 1, wobei die geformte
isolierende Struktur ein Griff, ein Querriegel oder ein Auslöseriegel ist, welcher
ein Teil im Inneren des Schalters ist.
6. Eine isolierende Struktur für einen Schalter, wobei die isolierende Struktur ein Formartikel
aus einem organischen Verbundstoffmaterial ist, welches 25 - 27 Gew.-% Nylon 6, 23
- 25 Gew.-% Nylon 66, 6 - 8 Gew.-% eines Ionomers eines Polyolefins und 42 - 44 Gew.-%
eines Verstärkungsmaterials umfaßt.
7. Die isolierende Struktur für einen Schalter wie in Anspruch 6, wobei das organische
Verbundstoffmaterial 26 Gew.-% Nylon 6, 24 Gew.-% Nylon 66, 7 Gew.-% eines Ionomers
eines Polyolefins und 43 Gew.-% eines Verstärkungsmaterials umfaßt.
8. Die isolierende Struktur für einen Schalter wie in Anspruch 7, wobei das Verstärkungsmaterial
nicht mehr als 0,6 Gew.-% eines Oxids eines Metalls aus der Gruppe 1A des Periodensystems
bezogen auf das Gewicht des Verstärkungsmaterials umfaßt.
9. Die isolierende Struktur für einen Schalter wie in Anspruch 7, wobei das Verstärkungsmaterial
Glasfasern umfaßt.
10. Die isolierende Struktur für einen Schalter wie in Anspruch 7, wobei die geformte
isolierende Struktur ein Gehäuse eines Schalters ist.
11. Die isolierende Struktur für einen Schalter wie in Anspruch 7, wobei die geformte
isolierende Struktur ein Griff, ein Querriegel oder ein Auslöseriegel ist, welcher
ein Teil im Inneren des Schalters ist.
1. Structure isolante pour un commutateur où la structure isolante est un article moulé
d'un matériau composite organique qui comprend 35 à 39% en poids de nylon 6, 8 à 12%
en poids de nylon 66, 1 à 3% en poids de nylon MXD-6, 7 à 9% en poids d'un copolymère
d'éthylène/α-oléfine, et 40 à 45% en poids d'un renforcement.
2. Structure isolante pour un commutateur selon la revendication 1, où ledit renforcement
ne contient pas plus de 0,6% en poids d'un oxyde d'un métal du Groupe 1A du Tableau
Périodique sur la base du poids du renforcement.
3. Structure isolante pour un commutateur selon la revendication 1, où ledit renforcement
comprend une fibre de verre.
4. Structure isolante pour un commutateur selon la revendication 1, où ladite structure
isolante moulée est un logement d'un commutateur.
5. Structure isolante pour un commutateur selon la revendication 1, où ladite structure
isolante moulée est une poignée, un élément de barres croisées ou une barre d'enclenchement
qui est une partie à l'intérieur d'un commutateur.
6. Structure d'isolement pour un commutateur où la structure d'isolement est un article
moulé d'un matériau composite organique qui comprend 25 à 27% en poids de nylon 6,
23 à 25% en poids de nylon 66, 6 à 8% en poids d'un ionomère de polyoléfine, et 42
à 44% d'un renforcement.
7. Structure isolante pour un commutateur selon la revendication 6, où ledit matériau
composite organique comprend 26% en poids de nylon 6, 24% en poids de nylon 66, 7%
en poids d'un ionomère d'une polyoléfine, et 43% en poids d'un renforcement.
8. Structure isolante pour un commutateur selon la revendication 7, où ledit renforcement
ne contient pas plus de 0,6% en poids d'un oxyde d'un métal du Groupe 1A du Tableau
Périodique sur la base du poids du renforcement.
9. Structure isolante pour un commutateur selon la revendication 7, où ledit renforcement
comprend une fibre de verre.
10. Structure isolante pour un commutateur selon la revendication 7, où ladite structure
isolante moulée est un logement d'un commutateur.
11. Structure isolante pour un commutateur selon la revendication 7, où ladite structure
isolante moulée est un poignée, un élément de barres croisées, ou une barre d'enclenchement
qui est une partie à l'intérieur d'un commutateur.