JPS585298Y2 - Shrinkable articles for electrically insulating objects - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shrinkable article for electrically insulating objects to be insulated, and in particular to an article suitable for making insulators used in high voltage fields.

In the high-voltage field, insulators (or insulators) are used, for example to support overhead power lines, in which case the insulation is compressed or in tension, and also, for example, in substation cabinets and transformers. In the case of switchgear bushings, it also provides a satisfactory leakage distance between high-potential and grounded equipment parts.

The outer surface of the insulation used as described above is generally provided with a number of sheds or protrusions, thereby increasing the creepage distance.
ce) and the flood over voltage are increased and leakage current is sensed.

These protrusions also constitute a number of protected areas that serve to improve the overall performance of the insulation.

As is well known to those skilled in the art, a tongue is a member that projects outwardly from the surface of an insulation and extends along its circumference to define a circumferential rib, skirt or fin on the insulation.

Traditionally, insulators of this type have generally been made from an insulating material such as porcelain or, in the case of suspension insulators, glass.

Relatively small units, such as IIKV and 33KV bushings for 33KV insulators and transformers and switchgear, are made from a single unit, the bushings being hollow so that they carry high potential metal components. being allowed to accept.

As size and shape complexity increases, single-piece insulation becomes more difficult to fabricate, and these insulations typically
Made using a number of separate units.

These units, in the case of bushings and stand-ins,
They are generally glued together to form a complete structure and, in the case of suspension insulators, are typically joined by metal fittings that are glued to glass or porcelain.

Insulators made as described above are advantageous in that relatively inexpensive materials are used, but they are disadvantageous in that they are expensive to manufacture, heavy, and relatively fragile.

In recent years, proposals have been made to make insulators from plastic materials.

The most commonly used material is epoxy resin,
Insulators or insulator components are made by casting or molding methods.

Thus, for example, British Patent Specification No. 1,345,5
No. 66 describes a method in which a central rod and a desired number of lobes are formed in one piece from a plastic material.

However, such one-piece molding methods have the disadvantage that different molds are required for each component, and therefore, if the prongs are made separately from the central rod and any desired It would be advantageous if it could be disposed on an insulating material.

Additionally, if the tabs are made separately from the body of the insulator, these tabs and, if desired, the outer surface of the insulator may be made of a material different from that used for the body of the insulator. It is possible to make it from

Thus, for example, a material with relatively poor electrical properties, even if it is otherwise suitable for use as an insulator (e.g. because of its cheapness and/or light weight), may be used as a non-tracking insulator. It can be used to make the body of the insulator if it is provided with an outer surface and a protrusion.

Proposals have been made to create an insulator by bonding a number of independent protrusions to a glass fiber core using a bonding agent.

For example, British Patent Specification No. 1.29.2, 276. The issue has been disclosed in which a large number of gods, a thermal contraction, to the center supporters have been disclosed.

However, even when heat-shrinkable protrusions are used,
The fabrication and assembly of a large number of separate protrusions inevitably takes a lot of time and leads to undesirable quality variations in the final product.

It is therefore considered advantageous if these projections are formed as seven parts of the outer jacket and are connected to the central support as a single unit.

However, attempts have been made to create an insulator with an outer jacket by molding a tubular member with multiple protrusions, transforming the member into a heat-shrinkable shape, and then shrinking it around the insulator. When Applicant conducted this, air was trapped between the tubular member and the insulator and the protrusions were deformed, and these protrusions were no longer located at right angles to the surface of the fuse, resulting in failure. Ta.

Such deformations occur randomly, with the protrusions forming an acute angle to the longitudinal axis of the tubular member, while the protrusions forming an acute angle with the result that the lightest appearance is unsatisfactory. Instead, in some cases, the outer ends of the tabs are so close to each other that an arc occurs between adjacent tabs.

Furthermore, the upwardly sloping lobes tend to collect water when the insulation is used outdoors, thereby impairing the electrical properties of the insulation.

It is therefore an object of the invention to provide an overcoat for objects to be insulated, which can be installed quickly and easily, and which, after installation,
The purpose is to provide something with a desired shape.

A second object of the invention is to provide a contractable article which has a particular desired shape before being transformed into a contractible state and which resumes said shape after being contracted around an object to be insulated. The purpose of the present invention is to provide an article that maintains its shape.

A third object of the present invention is to provide an electrically insulating covering with protrusions that can be coupled to an electrically insulating member to form an insulating surface of a desired shape on the member.

A fourth object of the invention is to provide a retractable insulating liquid membrane having a plurality of substantially vertical projections around an electrical component, such as a transformer bushing, stand insulator, or fuse. It is an object of the present invention to provide a device that can be contracted without substantially deforming the projecting piece.

A fifth object of the present invention is to provide composite structures, such as electrical insulators,
The object of the present invention is to provide a structure in which Rokko has a special feature and a desired shape, and a method for making such a composite structure.

In the present invention, a "shrinkable article" means that the article is dimensionally unstable while being stored and handled, and can maintain this unstable condition, but can be deformed when desired. It refers to an article that can be contracted without applying any force, and shrinking the article in this way is referred to as ``shrinking'' the article or ``shrinking'' the article.

Shrinkable articles remain dimensionally unstable until some specific action is taken to induce contraction.

Examples of such treatments include adding solvents (which may, for example, act to soften rigid components of the article) and making the article elastic to a contractable condition. The rigid member that is present may be removed.

In one preferred embodiment of the invention, the particular treatment for inducing said shrinkage is heating the article, in which case the article is said to be "heat-shrinkable."

The present invention is a collapsible article for electrically insulating an object to be insulated, the article comprising an elongated hollow member and a length extending outwardly from the hollow member. a plurality of protrusions substantially perpendicular to an axis of direction, and when the article is contracted to such an extent that there is only a small amount by which the article can be further contracted, the protrusions is substantially perpendicular to the longitudinal axis of the hollow member.

The invention also provides for outwardly applying an article according to the invention which has contracted to such an extent that once the object to be insulated has been removed, the article can be further contracted by a small amount of solder. A composite structure having an object to be insulated is provided.

The degree to which the article shrinks as described above is such that, if the object were removed and the article was completely deflated, there would be no substantial change in the angle between the protrusion and the longitudinal axis of the article. be made into

The maximum degree of shrinkage that falls within the "small" range will of course vary from article to article, but the limits are readily determined by simple routine experimentation.

The present invention further provides for positioning a retractable, hollow, elongated electrically insulating article having a plurality of outwardly facing protrusions substantially perpendicular to the longitudinal axis around an object to be insulated, and positioning the article on the object. an insulator, characterized in that the article can be further contracted by only a small amount and the protrusions are substantially perpendicular to the longitudinal axis. Provides a way to create objects.

Additionally, the present invention forms an elongate hollow article having a plurality of outwardly directed protrusions substantially perpendicular to the longitudinal axis, expands the inner diameter of the article to convert it into a contractible state, and converts the article into a contractible state. When the protrusion is approximately perpendicular to the longitudinal axis of the article, and when the article has contracted to such an extent that there is only a small amount by which the article can be further contracted, the protrusion is approximately perpendicular to the longitudinal axis of the article. To provide a method for making a shrinkable article, characterized in that the shape of the article is substantially perpendicular.

As mentioned above, the article of the present invention is hollow and has a plurality of outwardly directed protrusions.

These protrusions preferably extend continuously over the entire circumference of the article.

The projection is preferably integral with the article body.

In other words, it is preferable that the article has a solid shape as a single piece.

The article of the present invention may be made by molding.

Thus, each of the protrusions is approximately perpendicular to the longitudinal axis of the article in its "as-molded" shape (ie, fully collapsed shape).

The expression "right-angled" is to be understood to mean all configurations in which the mold can be separated only longitudinally and removed from the insulating member without substantially deforming the projection.

When a hollow shrinkable article shrinks in the absence of an object to be insulated by this article, said article shrinks until it reaches a dimensionally stable state in which further shrinkage is no longer possible.

However, if said shrinkable hollow article is placed around an object to be insulated, the outer dimensions of said object are such that said hollow article is dimensionally stable (fully deflated). The hollow article is prevented from shrinking to the dimensionally stable state by the object to be insulated.

In this specification, a state in which the article is prevented from shrinking to a completely contracted state as described above is referred to as an "incompletely contracted state."

As is clear from the above description, an article in an incompletely contracted state will not survive if the object to be insulated (which is preventing the article from fully contracting to a dimensionally stable state) is removed. If it were, it would be possible to contract it further.

In the article of the invention, the inner diameter of the contracted article when it is contracted in the absence of the object to be insulated is very slightly smaller than the outer diameter of the object.

These eugenic dimensional differences, consisting of both the inner and outer diameters, are such that if these two dimensions were to be the same, the article would not exert any lateral contractile force on the object; This is necessary because it can be relatively easily removed from the article.

However, by ensuring that the dimensional difference is small, the article is subjected to a minimum degree of incomplete shrinkage upon installation (i.e., nearly returns to its original dimensions as formed);
It can thus be ensured that there is little or no tendency for the projections to be deformed by internal stresses in the article.

and, if the article is heat-shrinkable and made of a material with a high coefficient of thermal expansion compared to the coefficient of thermal expansion of the object to be insulated, when the article is contracted and comes into contact with said object. The force between the article and the body is effectively a force at the contraction temperature: in other words, at the contraction temperature the article is at the same temperature as the original (as opposed to room temperature). has virtually the same dimensions as it would have had in the heat-shrinkable state, so virtually no stress is generated from the deformation to the heat-shrinkable state, and therefore there is no tendency for the prongs to be deformed during installation. It doesn't happen.

While the recommended difference between the outer diameter of said object and the inner diameter of a fully deflated article is determined according to the conditions, the internal linear dimension or inner diameter of a fully deflated article is calculated based on the internal dimensions. When reduced, it is preferably reduced by a percentage not exceeding 13% compared to the external linear dimension or diameter of the object.

However, if this dimensional difference is too small, it is made of a material whose coefficient of thermal expansion is higher than that of the object.

There is a risk that the heat-shrinkable article will not contact said object at the shrinking temperature, thus allowing air to be trapped between the article and said object.

For such heat-shrinkable articles, the difference between the linear dimensions is preferably two or more.

Advantageously, the inner surface of the article of the invention is configured to facilitate the escape of air between the article and the object to be insulated during contraction.

Thus, for example, the inner surface can be provided with one or more longitudinally extending grooves.

Alternatively, the cross-section of the inner surface of the article in its collapsible state is different from the cross-section of the object, defining a plurality of passageways along which air can be can make it possible to escape.

Thus, for example, the article may have a polygonal inner surface (such as a vine formed by the use of a mandrel with a polygonal outer surface extending the article), but the object may have a generally cylindrical outer surface. It can be made to have.

The hollow article used according to the invention exists in at least three different states during the period from the time of its manufacture until the time it is finally attached to the object to be insulated.

That is, they have a substantially dimensionally stable condition when the hollow article is molded and a first contraction large enough to allow the inner diameter of the hollow article to slide over the object to be insulated. a second collapsible state that is contracted around said object so as to form a composite structure, but is prevented by said object from fully contracting to its original dimensionally stable state; state.

In said second collapsible state, the hollow article is said to be partially deflated or, as defined in the previous paragraph, in an "incomplete deflated state", which according to the invention is partially deflated. is kept to a minimum.

Advantageously, the hollow article is such that its shrinkage is effected by heating, but if desired it may be caused by a solvent or by a rigid member holding the article in a shrinkable condition. It can also be done by removing a rigid member.

The degree of expansion of the hollow article from a substantially dimensionally heat-stable state to a first heat-shrinkable state with the result of increasing the inner diameter of the hollow article may be reduced, e.g., up to 13%; Alternatively, it can be made larger.

Preferably, if the degree of expansion is small, and preferably also if it is large, outward projections, e.g.
is prevented from moving appreciably from the orthogonal position during the expansion process.

This can be done by mechanical means, for example by tightening the projections or, if a plurality of external projections are provided, by bringing them into abutting relationship with said external projections. This can be achieved by using a comb-shaped device with plates that can be folded.

Although the invention is not limited to particular types of articles and objects to be insulated, the present invention can be applied to electrical cables, or electrical components such as fuses, transformer bushings, or chassis. It is particularly useful for providing a piece-structured shell member.

As previously mentioned, for ease of manufacture, these lobes are perpendicular to the longitudinal axis of the insulator.

These squared lobes also have the advantage that they provide a more orderly appearance than slanted lobes when multiple insulators are arranged at different angles to each other.

Also, if the article of the invention is used to cover insulation that is to be used in a vertical position, the article can be used with either side up.

If sloped lugs are used, they will have to slope downward to avoid collecting rainwater.

Examples of materials that can be used for articles of this invention include:

(a) silicone polymer, non-silicon polymer, 5i-
0-8i group-containing fillers treated with reinforcing silanes.
(See British Patent Specification No. 1,284,082) (b) Avoid silicone polymers and fluorinated hydrocarbon polymers; (c) alumina trihydrate as a non-tracking filler; (British Patent Specification No. 1.303,
432) Preferred compositions are those described in (c) above, where the non-tracking system consists of alumina trihydrate and an "active" metal oxide.

Said active metal oxide is an oxide or a mixture containing an oxide or a mixture of oxides, comprising a transition element or at least one element selected from the lanthanide series or the actinide series. .

The active metal oxides provide an improved non-tracking effect, thus reducing the required loading of the alumina trihydrate filler (UK Patent Specification No. 1,337).
, No. 951).

The material used must, of course, be capable of being converted into a heat-shrinkable state, but the expert will have no difficulty selecting a polymer or mixture of polymers such that this conversion is achieved. .

If desired, an adhesive can be used to adhere the article of the invention to the object to be insulated and/or at least a portion of the surface of the article that contacts said object may include a stress-relieving material or layer, That is, materials or layers can be provided which serve to reduce the electrical stresses present in areas of the high voltage element, for example at the ends of the screen of the high voltage cable.

Suitable adhesives include, for example, epoxy resins (hot-curing or cold-curing) and polyesters, as well as silicone-containing adhesives, especially those with non-tracking properties, which epoxy resins and polyesters can be used with fillers. It can be used with or without addition.

Other suitable adhesives include hydrocarbon copolymers containing at least one polymerizable double bond.
lymer) and carboxylic acid groups (which may be in the form of derivatives, such as esters or anhydrides), as well as copolymers of compounds containing polymerizable double bonds.

Examples of such copolymers are ethylene/vinyl acetate copolymers, ethylene/ethyl acrylate copolymers, methyl vinyl ether/maleic anhydride copolymers and preferably methyl.

Copolymers of vinyl acrylic esters and maleic anhydride may be mentioned.

The stress-relieving material or layer is preferably a material or layer with linear or preferably non-linear electrical resistance, is dimensionally stable, or has a viscosity of not more than 10 cp at 25°C. Upper amorphous substances (e.g.
consisting of a mastic-like substance).

An example of a suitable stress relief material is British Patent Specification No. 1,433.
, No. 129, No. 1,470,501, No. 1,47
No. 0,502, No. 1,470,503 and No. 1
, 470,504, the contents of which disclosures are incorporated herein by reference.

Stress relief as well as anti-tracking aspects can be combined in the articles or composite structures of the present invention, as described in British Patent Specification No. 1.526,397.

Hereinafter, the present invention will be explained in more detail by way of examples with reference to the accompanying drawings.

Referring now to the drawings, FIG. 1 is a longitudinal cross-sectional view of an article, designated generally at 10, which includes a longitudinally extending central portion 11 and a structure in which the article 10 can be easily molded. It has a number of protrusions 12 that are substantially perpendicular to the central portion 11.

In FIG. 1, article 10 is in a dimensionally heat stable configuration.

A heat shrinkable form 10' of article 10 is shown in FIG.

In this shape, the article has an inner diameter of shape 10 and a diameter of 10'.
(e.g., a fiberglass rod 13 with a metal end cap 14 shown in FIG. 3) having an outside diameter between an inside diameter of As shown in FIG.

As can be seen from the figures, the lug 12 is substantially perpendicular to the central portion 11 in all three figures.

According to the invention, the inner diameter of the central portion 11 and the outer diameter of the rod 13 are selected such that such a substantially orthogonal arrangement is obtained in the composite product (FIG. 3).

Articles and composite articles or composite structures according to the invention are illustrated in the following examples: Examples 1-3 Three articles having a plurality of lobes were molded from electrically insulating material.

The electrically insulating material was a crosslinked mixture of dimethyl silicone elastomer, low density polyethylene, and ethylene-ethyl acrylate copolymer containing alumina trihydrate and red iron oxide.

On each side, lugs, essentially the same as those shown in FIG. 1, are substantially perpendicular or at right angles to the longitudinal axis of the article and It was symmetrical about a vertical or right-angled plane.

Each article was converted to a heat-shrinkable shape by heating, expansion with a mandrel, cooling, and removal of the mandrel.

Each heat-shrinkable article was then placed around a suitable cylindrical fuse and shrunk into tight contact with the fuse.

In a separate experiment, the same heat-shrinkable articles that were shrunk around the fuse were heated without placing an object to insulate them to determine their fully shrunk diameter.

The inner diameter of the heat-shrinkable article and the outer diameter of the fuse as well as the inner diameter of the fully shrunk article are shown in the table below.

The table also shows the percentage of incomplete deflation of the article when deflated about the fuse.

This percentage was calculated according to the following formula: In each case, the lobes of the articles contracted around the fuse remained substantially perpendicular to the longitudinal axis of the articles.

Examples of embodiments of the present invention and related methods and structures are as follows: (1) An article as claimed in the claims of the utility model registration, in which the protruding piece is integrated with the rest of the article.

(2) The article according to claim 1 of the utility model registration claim or embodiment 1, which is heat-shrinkable.

(3) The inner surface of the article has at least 1' longitudinally extending deformation parts, so that when the article is contracted, air can easily escape from between the article and the object to be insulated. Claims or embodiments of the article according to item 1 or 2 of the utility model registration claim.

- (4) An article according to any one of the claims or embodiments 1 to 3 of the utility model registration claim, in which the inner surface of the article is shaped so that air can easily escape from between the article and the object to be insulated when it contracts. .

(5) The article is heat-shrinkable and the internal dimensions of the article are such that at the temperature at which the article is heated to cause its contraction, the force between the article and the object to be insulated is approximately zero. An article according to any one of the utility model claims or embodiments No. 1 to 4.

(6) Scope of Utility Model Registration Claims or Embodiments 1 to 1 in which the article is deformed from its original shape to a contractible shape, and the internal dimensions of the article in the original shape are slightly smaller than the external dimensions of the object to be insulated. 6゜ (7) Any of the articles of item 5 (7) The linear internal dimensions caused by contraction in the absence of the object to be insulated, calculated based on these, are not more than 13% smaller than the linear external dimensions of the object. An article according to any one of the utility model claims or embodiments No. 1 to 6.

(8) The article of embodiment 7, wherein the linear internal dimension of the article is 2% to 13% smaller than the linear external dimension of the object to be insulated.

(9) The article according to any one of the claims or embodiments 1 to 7 of the utility model registration, which is made of a non-tracking material.

00) Scope of utility model registration claims or embodiments 1 to 9
A composite structure comprising an object to be insulated, the outer surface of which is covered with the article according to any one of the preceding paragraphs, and the article has only a slight degree of incomplete shrinkage.

0υ Composite structure according to embodiment 10, wherein the object to be insulated is a fuse body, a bushing or a pedestal.

(12) A method of providing an object provided with an insulator, the method comprising:
positioning a retractable, hollow, elongated electrically insulating article having a plurality of outwardly facing projections substantially perpendicular to the longitudinal axis around an object to be insulated and contracting the article onto the object; , in which the article has only a small degree of incomplete contraction during this contraction, and the protrusion is approximately perpendicular to the longitudinal axis of the article.

(13) A method of making a contractible article as claimed in the claims, comprising: forming an elongated hollow article having a plurality of outwardly directed protrusions substantially perpendicular to a longitudinal axis;
Increasing the internal dimensions of the article to convert it to a contractible state in which the lobes are approximately perpendicular to the longitudinal axis of the article and the article has only a small degree of incomplete contraction. A method in which the projecting piece is approximately perpendicular to the longitudinal axis of the article when contracted to a certain extent.

(14) The method of embodiment 13, wherein comb-like means abutting the tabs prevent any movement of the tabs from their perpendicular position while increasing the internal dimensions of the article.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a coating for insulation kept in its thermally stable state; FIG. 2 is a longitudinal section of the coating of FIG. 1 in its expanded heat-shrinkable state. Vertical sectional view; 3rd
The figure is a longitudinal cross-sectional view of the covering of FIG. 2 contracted around the fuse. In the drawings, 10 indicates an "article"; 11 indicates a "center portion"; 12 indicates a "projection"; 13 indicates a "rondo"; and 14 indicates an "end cap".

Claims (1)

[Scope of utility model registration request] A retractable article for electrically insulating an object to be insulated, the article comprising an elongated hollow member and an elongated hollow member extending outwardly from the hollow member along the longitudinal axis of the hollow member. a plurality of substantially vertical projections, and when the article is contracted to such an extent that there is only a small amount by which the article can be further contracted;
The article wherein the projection is substantially perpendicular to the longitudinal axis of the hollow member.