JPH0158603B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for manufacturing inorganically insulated cables, i.e. cables of the type having at least one conductor insulated from a surrounding metal sheath, in which inorganic insulating powder is One or more conductors are insulated from other conductors.

Inorganically insulated cables generally consist of a preformed metal tube with one or more conductor rods, the metal tube is filled with inorganic insulation powder, and the insulating powder is tamped into the tube around the conductor. and/or by pulling the filled tube through one or more dies to elongate it, compacted tightly by vibration.

According to the invention, an improved method of manufacturing mineral insulated cables consists of the following steps.

(i) charging a first tube having at least one conductor rod with an inorganic insulator so that a portion of the length of the tube is filled; and (ii) filling the first tube with an inorganic insulating material. (iii) a second tube extending along a portion of its length; (iv) filling the unfilled portion of the first tube and the second tube with inorganic insulation so that at least a portion of the length of the second tube is filled with the inorganic insulation; (v) stretching said end of the first tube and said second tube over at least the filled portion in one continuous operation.

The unstretched length of the at least one conductor rod (before undergoing the stretching process) is longer than the combined unstretched length of the first and second pipes, and the second pipe is Preferably, it is advanced through the end of the rod or rods surrounding it to the location where both tubes are to be welded.

In another embodiment of the invention, the at least one conductor rod of the first tube is butt welded to the next one or more conductor rods at a location remote from where the tube is welded, such that the at least one conductor rod of the first tube Forming a continuum of conductive rods of books,
A second tube is then advanced over the distal end of the conductor rod and around the conductor rod to the location where the tube is to be welded.

In another embodiment of the invention, at least one conductor rod is butt welded to the next rod or rods in close proximity to where the tube is welded to form a series of at least one conductor rod. .

The rod or rods are then preferably supported within the second tube as the second tube is advanced toward where the tubes are to be welded.

The method preferably also comprises the following steps. (a) welding the unstretched end of the second tube to a third tube surrounding at least one series of conductor rods; and (b) welding the unstretched end of the second tube to the third tube. (c) drawing the remaining portion of the second tube and the third tube along at least the filled length in one continuous operation;

Steps (a), (b), and (c) are repeated using the other tube or tubes.

Preferably, one or more conductor rods are extended or a third or subsequent tube is arranged around the conductor rod in the same manner as the second tube.

The insulation may be charged to the tube as a free-flowing inorganic insulating powder and then compacted by tamping or vibrating the tube. For example, blocks made in advance of solid inorganic insulating material with vertical holes are inserted one after another into a pipe, and the conductor rods are passed through the blocks in alignment with the vertical holes.

The present invention therefore provides a simple method of manufacturing mineral insulated cable of a desired length as a single, unconnected piece.

Also, when making a number of cables of the same length that can be drawn by conventional methods from a single tube, it is possible to cut a number of desired lengths from a continuous long single cable made by the method of the present invention. , reducing material consumption. This means that the amount of material that is trimmed from both ends of a single length of cable of the invention (from which multiple cables of desired lengths can be obtained) is equal to This is because it is the same amount that is cut off from the book.

The preformed tubes used in the method of the invention may be formed by drawing or made by suitably forming tapes and welded together as described and claimed in British Patent Nos. 1,554,859 and 1,554,860. Ru.

According to the present invention, (i) charging means for charging an inorganic insulating powder that can freely flow into a tube in which at least one conductor rod is disposed; (iii) welding means for welding the partially stretched tube to a second tube, the welding means being intermediate between the charging means and the stretching means; An improved apparatus for manufacturing disposed inorganic insulated cables is provided.

Moreover, it is preferable that the welding means is an orbital TIG welding machine.

Therefore, conventional mineral insulated cable manufacturing equipment can be readily modified to implement the present invention. Additionally, devices embodying the invention occupy substantially the same space as prior art devices. The cost of retrofitting existing equipment or installing new equipment is low with the present invention.

In order that the invention may be better understood, an example will be given and reference will be made to the accompanying drawings, FIGS.

A stainless steel starting tube 1 is swaged at its front end and sent from a source 2 to a mounting station 3 where it is initially mounted onto a guide tube 4 . Two inner tubes (not shown) of the conductor enclosure each containing a conductor rod 5 are inserted into the guide tube. The starting tube 1 is supported on its outside by an automatically operated clamp 6. The front end of the conductor rod 5 emerging from the guide tube is attached to a plug 7 which is press-fitted into the bent end of the tube 1. The bent end of the starting tube 1 is connected to a guide die 9 attached to a spacer ring 10 supported by a sealing die 11.
It is held by a chuck 12 through a metal die box 8 containing a die.

A feed stage 13 for selectively supplying either an inert gas or an inorganic insulating powder is mounted near the top of the guide tube 4 to deliver freely flowing molten or caustic magnesia to the guide tube, all the while supplying the starting tube 1. is vibrated by two air hammers 14. The vibrations encourage the insulating powder to flow downstream through the guide tube, concentrating the powder in the starting tube prior to drawing. Figure 1 shows the installation in this process.

Vibration occurs while the tube is drawn through a closed die and wound onto a driven take-up reel 15, and a constant level of lubricating oil is maintained in the die box 8 during the drawing operation. When the entire top part (approximately 200 mm) of the tube 1 is stretched by the die box 8 and the rear part of the tube 1 passes the guide tube 4, the rotation of the take-up reel 15 and the vibration by the air hammer 14 are stopped and the stretching operation is performed. is interrupted. Excess powder flowing from the guide tube is removed by suction.
Also, loose powder to a depth of about 12 mm is removed from the starting tube 1.

The supply table 13 is moved and the guide tube 4 is moved to the clamp 1.
6 and the clamp 6 is loosened so that the second tube 17 can be fed from the source 2 onto the guide tube 4 . The length of each starting tube from source 2 is clamp 6
and the clamp 16, so that when a new starting tube is lowered onto the guide tube 4, this starting tube comes under the clamp 6, so that the clamp 6 can support the guide tube. . Thus clamp 1
6 is loosened and the new starting tube is lowered and fitted onto the top of tube 1.

The feed stand 13 is now again mounted on top of the guide tube 4 and inert gas is fed into the feed stand at low pressure to drive out the oxidizing gas from the space around the end of the tube. An orbital welder 18 is mounted around the tube ends to TIG gas weld both tube ends together (see Figure 2).

Each weld is visually inspected to determine if there is a normal weld overlap in that the weld is flat with respect to the connected tube surface and can be subsequently stretched well. However, if the weld is protruding or recessed (due to excessive argon internal pressure), the insulation will be uneven at the weld during the next stretching process, and the insulation will be uneven.
Or damage occurs to the weld. If it is deemed unsafe, the weld is cut out and a new end is welded.

After the weld has cooled, welder 18 is removed and the expulsion gas is turned off. The tube 17 is filled with inorganic insulating powder from the feed stage 13 to the guide tube 4, and the remaining part of the tube 1 and part of the tube 17 are extended through the die box 8.

This process is repeated with the unstretched top of tube 17 and with new tube from source 2, as many times as desired.

A long continuous conductor rod 5 is formed by resistance butt welding individual conductor rods. Each tube passes from the supply source 2 to the guide tube 4 over the tip of the conductor rod 5.

[Brief explanation of drawings]

FIG. 1 is a schematic exploded elevational view of the installed state in the first step of the manufacturing method of the present invention, and FIG. 2 is an elevational view similar to that of FIG. 1 in the installed state of the next step. 1... Starting tube, 2... Supply source, 3... Mounting part,
4... Guide tube, 5... Conductor rod, 6, 16... Clamp, 7... Plug, 8... Die box, 9... Guide die, 10... Spacer ring, 11... Sealing die, 12... ...chuck, 13...supply stand, 14...
...Air hammer, 15...Take-up reel, 17...
Second pipe, 18...Welding machine.

Claims (1)

[Scope of Claims] 1. When an inorganic insulator is charged into a tube in which at least one conductor rod is disposed at a predetermined position inside the tube away from the inner wall, and when the tube is stretched, (i) at least one conductor (ii) filling a portion of the length of the first tube with the inorganic insulation by charging the first tube with the rod in place therein; (iii) an unstretched portion of the first tube into a second tube surrounding a continuous portion of said at least one conductor rod disposed in the first tube; (iv) charging the unfilled portion of the first tube and the second tube with inorganic insulation, filling at least a portion of the length of the second tube with the inorganic insulation; (v) a method for producing an inorganic insulated cable, comprising the step of stretching the remaining end of the first tube and the second tube at least along the filled length in one continuous operation. 2. Step of inserting at least one conductor rod into the first tube before charging the inorganic insulator and stretching the length of the conductor rod before the stretching step of the combined first and second tubes. 2. A method as claimed in claim 1, characterized in that the length is longer than the previous length. 3. Butt welding the at least one conductor rod of the first tube to the next conductor rod at a location away from where both tubes are welded to form a continuous rod of at least one conductor rod. A method according to claim 1, characterized in that: 4 The second pipe is passed around the tip of one or more conductor rods, surrounds the conductor rods, and is advanced toward the place where the first pipe and the second pipe are to be welded. The method according to any one of claims 1 to 3. 5. characterized in that when the second pipe advances toward the location where the first pipe and the second pipe are welded, it supports the next one or more conductor rods within the second pipe. A method according to claim 3. 6 (a) welding the unstretched end of the second tube to a third tube surrounding at least one continuous rod of the conductor rod; (b) welding the unstretched end of the second tube to the third tube; Claim 1, characterized in that: (c) the remaining portion of the second tube and the third tube are stretched in one continuous operation along the filled length; The method according to any one of Items 1 to 5. 7.Add one or more pipes to the above (a)(b)(c)
7. The method according to claim 6, wherein the steps are repeated. 8. A charging means for charging an inorganic insulator into a tube in which at least one conductor rod is disposed at a position distant from the inner wall, and a tube at least partially filled with the inorganic insulator. an inorganic insulation comprising a stretching means for stretching the partially stretched tube to a second tube, and a welding means for welding the partially stretched tube to the second tube is located between the charging means and the stretching means. Cable manufacturing equipment. 9. The apparatus according to claim 8, wherein the welding means is an orbital TIG welding machine.