JPS6016902B2 - Polymer concrete with cast female threads - Google Patents

Description

[Detailed Description of the Invention] To attach electric wires and other electrical members to an insulating molded body,
Usually, the electrical member is inserted into an insulating molded body and then tightened.

This insulating molded body is usually made of porcelain, and it is extremely difficult to cut threads on such a porcelain molded body, so even if there is an insulating molded body with threads cut, it is extremely difficult to cut threads on such a porcelain molded body. rare. Even if it is made for a special purpose,
Bolts or other fasteners inserted into the threads will easily wear down the threads, allowing the attached electrical components to be easily removed from the insulator body. Normally, in order to attach an electrical member to porcelain, it has been common practice to cement a metal cap to the insulator and attach the electrical member to the metal cap. The metal cap method has the following three drawbacks.

That is, the conductive metal is spread over a large area, and
This metal part occupies the most expensive part of the insulator structure and causes various problems due to the different thermal properties between metal and porcelain. Despite these drawbacks, the metal cap is widely used as an essential item.
It has now been found that if the insulating molding is made of a special material and the threads are produced in a special way, the metal cap and its attendant drawbacks can be completely eliminated.

The threaded portion made according to the invention is stronger than the remaining portion of the insulating molding. Therefore, an object of the present invention is to provide an excellent insulating molded body having at least one or more threads.

The strength and abrasion resistance of the threaded portion according to the invention are so great that the metal caps conventionally used can be omitted. These and other objects will become clear from the description of the invention based on the accompanying drawings.

This invention relates to an excellent insulating molded body with threads.

In particular, the present invention relates to an excellent insulating molded body having at least one thread cast by vibration molding, characterized in that the molded body is molded from acicular aggregate and synthetic resin bond. Furthermore, the present invention relates to a method for manufacturing the insulating molded body. The polymer concrete of this invention is a mixture of hardening resin (hereinafter referred to as bond) and acicular aggregate. The polymer can be any Z-resistant, electrically insulating grade resin that, when cured, binds the acicular aggregates together and fills the pores. good. Therefore, epoxy resin, polyester resin, polyurethane resin, polyolefin resin, silicone resin, acrylic resin, phenol resin, etc. can be used. These polymers can be selected from commercially available products in consideration of their physical properties, electrical properties, hydrophobicity, caking properties, and ease of handling. A particularly suitable polymer is an electrically insulating epoxy resin. Those skilled in the art will readily understand that these resins can contain crosslinking agents that are effective at temperatures other than room temperature.

For example, in the case of epoxy resins, it is preferable to incorporate curing agents and catalysts such as acid anhydrides or amines that crosslink the epoxy resin at high temperatures. Furthermore, it is desirable to use a polymer having a modulus of elasticity after crosslinking in the range of about 1.4 to 7.times.1 k9/m.

This is because when a load is applied to the cast thread, it causes a slight deformation of the thread, which distributes the strain over the entire length of the engagement part of the thread, giving the thread maximum strength. It is from. Furthermore, as is clear from FIG. 3, when a load is applied to the screw thread, the spicules are subjected to compressive stress and shear stress, whereby maximum strength is achieved.

More than 50% of the aggregate is acicular. In particular, approximately 65~
Preferably, it consists of 75% acicular aggregate. Although any electrically insulating material available in acicular form can be used, ground electrically insulating porcelain has been found to be an excellent acicular material with all the required physical properties. Other ceramic aggregates such as steatite, alumina, titanate, spinels
), mullite (M-sides), sillim
Antes), Zircons, and/or other mineral aggregates can be used as long as they are available in, or can be processed into, acicular form.

As other aggregates, materials commonly used as fillers in synthetic organic polymer insulation materials can be used. In order to minimize the volume filled by the concrete bond, the materials making up the aggregate should be of various particle sizes.

For example, it is preferred to use at least two types of acicular aggregate with different particle sizes depending on the thread dimensions. Since the resin bond in polymer concrete is usually the most expensive material, it is desirable to keep the concentration of bond in the bond and aggregate mixture as low as possible.

Generally, the aggregate in the blend is about 70-95%, preferably about 80-90%.

The bond and aggregate must be mixed under reduced pressure to avoid large voids and air bubbles in the final product, and to ensure that the aggregate is sufficiently wetted by the resin bond. found.

Decompression degree of 27 inches Hg (Iso 5 legs Hg) or more, especially about 2
9 to 30 inches Hg (736 to 762 inches Hg) is preferred.

From an operational standpoint, it is preferable to mix the two under heating at a temperature below the crosslinking temperature of the resin bond.

When using an epoxy resin that crosslinks at about 15030C, temperatures of about 500 to 125 qC, particularly about 70 to 90C, are preferred.

The mixing time is not critical.

The optimal time can be easily determined by a simple desktop experiment.
The presence of a very small group of voids does not impair the insulating properties of the product, so vacuum casting is not necessary. However, if it is necessary to completely eliminate voids, vacuum casting may be performed. good.

The aggregate and bond are mixed in separate equipment and then the mixture is placed in a mold.

A suitable threaded member is set or inserted into the mold either before or after filling the mixture. According to the invention, the acicular aggregates in the admixture adjacent to the inserted externally threaded member or other mold surface are aligned parallel to each other and also parallel to the insert or mold surface. .

The compound in the threaded part will have needle-like particles aligned parallel to each other in that part, which gives the threaded part unexpected and surprising strength.

Said alignment of the granular aggregate particles in the vicinity of the insert is achieved by mechanical means, in particular by applying vibration, but may also be achieved by centrifugal flow casting or other means, in which the admixture hardens. In addition, it provides an alignment force to the acicular aggregate particles. In order to achieve the object of the present invention, it is preferable that the mixture vibrate relative to the externally threaded member.

Mechanical thread cutting does not achieve the thread strength of this invention. Another drawback is that it is difficult and expensive to manufacture due to the hardness of the aggregate. The amplitude of the vibration is not strict and can be freely set as long as it is not so strong that air is entrained in the mixture. Since this can be easily confirmed by observation, the optimum amplitude is determined by observation to give flow to the lump.

The vibration is preferably carried out at the same temperature as the mixing temperature of the aggregate and bond, but any temperature below the crosslinking temperature of the pound may be applied if desired. The amplitude time is a function of the vibration amplitude and temperature conditions. Vibration should be continued until at least the surface resin bond of the admixture is observed to flow, and preferably the flow is substantially complete. The phenomenon of bond extrusion on the surface of a vibrating mixture is similar to the phenomenon observed during vibration of Portland cement concrete.
After the vibration is completed, the mixture is heated to or above the crosslinking temperature of the bond. As is known, the formation of voids can be prevented by slightly pressurizing the mixture during crosslinking. The admixture can be fully crosslinked in the mold, or once the bond has gelled, it can be removed from the mold and crosslinked in an oven to increase mold utilization.

Two embodiments of the invention are shown in FIGS. 1 and 2. FIG. FIG. 1 shows a unitary structure of a solid station post insulator made of polymer concrete manufactured according to the process described above.

The embodiment of FIG. 2 shows an example of a porcelain station post insulator, the molded body 1 being made by known means and provided with a receptacle 2 suitable for receiving the insert 3 of the invention. is cemented in place with a suitable adhesive layer 4. The threads of this invention are preferably coated with a graphite or silver based conductive paint. This coating has the effect of dispersing electrical strain around the inserted metal bolt, and moistening the threads to facilitate insertion and removal.

Although there is no need to adhere to theory, it is believed that the reason why the threads produced by this invention have an abnormally high mechanical strength is due to the alignment of the acicular aggregates present in the threads of the concrete molded body. It is estimated that

FIG. 3 shows this special arrangement.

Photomicrographs of 1st, 2nd and 3rd notes of screw threads made according to the present invention using the recipe of Example 3 are shown in Figures 4, 5 and 6, respectively. The photo suggests that the above hypothesis is correct.

Although FIGS. 1 and 2 show a single thread cast, it is also possible to cast multiple threads into the compact if desired. Moreover, the tensile strength of the thread can be adjusted by changing the height of the thread. Next, the present invention will be explained in more detail based on examples.

Unless otherwise indicated, all parts and percentages in the specification and claims are by weight and temperatures are in degrees Celsius. [Example] Four types of station post insulators were manufactured according to the formulations shown in Table 1.

Aggregate (crushed porcelain and sand) and crosslinking agent-containing epoxy resin bond were placed in a Ross blender at 90q0
The mixture was mixed for 4 minutes under a vacuum of approximately 30 inches (76 inches) Hg.

150 qo mold including a male thread die coated with a molding agent
It was preheated to 100%, placed on a diaphragm, and started vibrating. The mold was filled with the mixture while vibrating. Then set the sprue to 25psi (
1.74k9/average) It was pressurized with air pressure. Heat the mold to 150℃
After heating at a constant temperature for 30 minutes, remove the station post and place it in an oven at 150 qo for 3 hours.
Completely crosslinked. All four formulations produced strong threads. Table 1: Balanced sample method using Biddle type corona bridge for insulators according to Example 2
A corona test was conducted using the following method.

No corona was generated up to 6 songs V, and at 70 KV, the insulator generated corona of 10 to 30 pC.

All these station post insulators are N class (20
It had a heat distortion temperature of 0oo) or higher. Machine bolts were inserted into the cast threads of each of the four types of station post insulators.

A tensile test was then conducted without unscrewing. In both cases, the insulator itself was destroyed before the screw threads were crushed. In station posts made using sand or other non-acicular fillers as aggregate, the threads were easily crushed, but the insulator itself was not damaged. Diameter 12.7 skin - 13 (25.4 number of ridges in willow) x ridge height 25.4 Diameter 3 with female threads
An inch (76 side) cylinder was manufactured according to the recipe of Example 3. Next, a bolt was inserted and a tensile test was performed. The tensile force required to fracture this cylinder was 8990 pounds (4045 k9). No damage to the threads was observed. It will be obvious that widely different embodiments of the methods and products of the invention may be made without departing from the spirit and scope of the invention.

The various embodiments disclosed herein are merely exemplary;
This invention is not limited to these.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of an insulator according to one embodiment of the present invention, FIG. 2 is a partial sectional view of an insulator according to another embodiment, and FIG. 3 is an enlarged partial sectional view of the insulator of the present invention. FIGS. 4, 5, and 6 are enlarged microscopic photographs of threaded portions according to the present invention, respectively. 1...Molded body, 2...Socket, 3...
...Insert, 4...Adhesive layer. 'E[E-J- QG・3・ZG-3- Rokuhan Semi Misaki Torohanagi Banichi Hirobo Sakara. song.

Claims (1)

[Scope of Claims] 1. A molded body made of acicular aggregate bonded by a crosslinked synthetic resin bond, the molded body containing at least one
A molded article having a plurality of threads, acicular aggregate particles in contact with the thread surface are aligned parallel to each other, and the particles are also aligned parallel to the thread surface. 2. The molded article according to claim 1, wherein the synthetic resin bond is made of epoxy resin. 3. The molded article according to claim 1, which has a plurality of threads. 4. The molded article according to claim 1, wherein the synthetic resin bond accounts for 5 to 30% by weight of the molded article. 5. The molded article according to claim 4, wherein the synthetic resin bond accounts for 10 to 20% by weight of the molded article. 6 The elastic modulus of the crosslinked synthetic resin bond is (1.4 to 7) x
The molded article according to claim 1, characterized in that the weight is 10^5 kg/cm^3. 7. The synthetic resin bond is made of epoxy resin, and 65 to 75% by weight of the acicular aggregate is made of electrically insulating porcelain,
The molded article according to claim 6, wherein the synthetic resin bond accounts for 10 to 20% by weight of the molded article. 8. The molded article according to claim 1, which is in the form of a station post insulator. 9. A molded article according to claim 1, which is in the form of an insert suitable for cementing into an electrical insulator. 10 A molded body made of acicular aggregate bound by a crosslinked synthetic resin bond, which has at least one thread in the molded body, and further has an acicular aggregate in contact with the surface of the thread. A method for producing a molded article in which aggregate particles are aligned parallel to each other and the particles are also aligned parallel to a thread surface, the aggregate and an uncrosslinked synthetic resin bond being bonded together at least twice.
mixing at a reduced pressure of 7 inches Hg (686 mm Hg) or more; and contacting at least one threaded die with a portion of the mixture to align acicular aggregates adjacent the threaded die parallel to each other. and then crosslinking the uncrosslinked resin bond. 11. A method according to claim 10, characterized in that the threads are vibration cast into the compact. 12. The method of claim 10, wherein the synthetic resin bond is 5 to 30% by weight of the mixture. 13 The synthetic resin bond accounts for 10 to 20% by weight of the mixture.
The method according to claim 12, characterized in that: 14 The degree of vacuum is 29 to 30 inches Hg (737 to 76
11. The method according to claim 10, wherein the temperature is 2 mmHg). 15. The method according to claim 10, wherein the acicular aggregate is made of electrically insulating porcelain. 16. The method according to claim 10, wherein the synthetic resin bond is an epoxy resin. 17 The elastic modulus of the crosslinked synthetic resin bond is (1.4 to 7)
11. The method according to claim 10, characterized in that the temperature is in the range of x10^5 kl/cm^3. 18 The synthetic resin bond is an epoxy resin, 65 to 75% by weight of the acicular aggregate is made of electrically insulating porcelain, and the synthetic resin bond accounts for 10 to 20% by weight of the molded body,
and the degree of vacuum is 29 to 30 inches Hg (737 to 762
(mmHg)
The method described in Section 7.