Title of Invention

A JIG FOR ENLARGING THE DIAMETER OF A RUBBER INSULATOR

Abstract

ABSTRACT The invention provides a jig for enlarging the diameter of a rubber insulator. [Problem] To provide a jig for enlarging the diameter of a rubber insulator unit, the jig having a structure in which the diameter-enlarging jib is split into pieces both in a direction perpendicular to the axis thereof and in a longitudinal direction thereof and which withstands an insertion force at the t.ime of insertion. [Solving Means] One pipe is split into pieces both in a direction perpendicular to the axis of the pipe and in a longitudinal direction of the pipe so that joints of the respective pieces obtained by splitting the pipe in the longitudinal direction are shifted from each other in a circumferential direction of the pipe. [Selected Drawing] Fig. 1

Full Text

The present invention relates to a jig for enlarging the diameter of a rubber insulator. Accordingly the present invention provides a jig for enlarging the diameter of a rubber insulator, while mounting to a connection portion between two cables, said jig comprising a pipe split into pieces both in a direction perpendicular to the axis of said pipe and in a longitudinal direcfion of said pipe so that joints of the respective pieces obtained by splitting said pipe in said longitudinal direction are shifted from each other in a circumferential direction of said pipe. The invention also provides a process for mounting a rubber insulator unit onto a connection portion between two cables with the jig as claimed in any one of the previous claims, comprising the steps of : inserting said jig into said rubber insulator unit while enlarging the diameter of said rubber insulator with the aid of said tapered tube; removing said tapered tube from said first pipe piece; locating said first and second pipe pieces, on which said rubber insulator unit has been mounted, around one of said cables; providing a conductor connection portion between insulator cores of said two cables; moving said first and second pipe pieces, on which said rubber insulator unit has been mounted, so that said rubber insulator unit is located around said conductor connection portion; removing said first and second pipe pieces from said rubber insulator unit such that said first and second pipe pieces are moved in opposite directions in said longitudinal direction, to thereby closely mount said rubber insulator unit onto said insulator cores of said cables; and removing said first and second pipe pieces from said two cable such that said first and second pipes pieces are respectively separated into semi-cylindrical pieces. [Brief Description of the Accompanying Drawings] Fig. 1 is an external appearance view of a specific example of the diameter-enlarging jig according to the present invention. Fig. 2(A) and 2(B) are explanatory views of joint portions of two pipe pieces obtained by splitting the pipe in a direction perpendicular to the axis of the pipe. Fig. 3 is a vertical sectional view of a main part of a plug-in type connection portion of a rubber/plastic electric power cable. Fig. 4 is a side view of a piece lA of a pipe piece 1. Fig. 5 is a sectional side view showing a jig constructed by pipe pieces 1 and 2 and a tapered tube 25. Fig. 6 is a partially sectional view for explaining a process for mounting a rubber insulator unit 13 onto the jig. Fig. 7 is a partially sectional view for explaining the process for mounting the rubber insulator unit 13 onto the jig. Fig. 8 is a partially sectional view for explaining a process for mounting the rubber insulator unit 13 onto electric power cables with the use of the jig-Fig. 9 is a partially sectional view for explaining a process for mounting the rubber insulator unit 13 onto the electric power cables with the use of the jig. Fig. 10 is a partially sectional view for explaining a process for mounting the rubber insulator unit 13 onto the electric power cables with the use of the jig. [Description of Reference Numerals] 1, 2 two pipes obtained by splitting a pipe in a direction perpendicular to the axis of the pipe lA, IB, 2A, 2B respective pieces of the pipe split in a longitudinal direction of the pipe 3 joint portion [Prior Art] Fig. 3 is a vertical sectional view of a main part of a plug-in type connection portion of a rubber/plastic electric power cable. In the drawing, the reference numeral 11 designates an insulated core of a cable having a plastic insulating layer of crosslinked polyethylene, or the like; 12, a connection portion of a cable conductor; and 13, a rubber insulator unit which is constituted by an inner electrode 13B of semiconductive rubber disposed in the inner circumferential portion of an insulating rubber portion 13A and an outer semiconductive layer 13C of semiconductive rubber disposed in the outer circumferential portion of the insulating rubber portion 13 A. The insulating rubber portion 13 A, the inner electrode 13B and the outer semiconductive layer 13C are integrally molded in advance. The rubber insulator unit 13 is formed so that its inner diameter is smaller than the outer diameter of the insulated core 11. Alternatively, the aforementioned rubber insulator unit 13 may be produced so that the outer semiconductive layer 13C is formed in the outer circumferential portion of the insulating rubber portion 13A after the inner electrode 13B is integrally molded in advance in the inner circumferential portion of the insulating rubber portion 13 A. In addition, a reference numeral 15 designates a stress relief member fixed to right and left insulated cores 11 across the conductor connection portion 12 so that a distance between the end faces of the right and left insulate cores 11 is maintained and that the connection portion 12 is prevented from being subjected to an excessive tensile stress. In forming the connection portion, the aforementioned rubber insulator unit 13 having a diameter enlarged by insertion of a pipe-like diameter-enlarging jig having an inner diameter larger than the outer diameter of a cable is inserted into the inner diameter portion of the aforementioned rubber insulator unit 13 so as to enlarge the inner diameter of the rubber insulator unit 13 in advance and this rubber insulator unit 13 is fitted onto one cable in advance before the connection of cable conductors. After the connection of the cable conductors of one and the other cables, the rubber insulator unit 13 is returned onto the conductor connection portion 12 and the diameter-enlarging jig is drawn out, so that the rubber insulator unit 13 is stuck closely onto the insulated core 11 by self-contracting force so as to form a connection portion insulating portion. [Problem to be solved by the Invention] In the aforementioned case, generally, a single pipe is used as the diameter-enlarging jig. Accordingly, in order to draw-out the diameter-enlarging jig after the rubber insulator unit containing the diameter-enlarging jig inserted therein is returned to the conductor connection portion after the connection of the conductors, it is necessary to cut and remove the diameter-enlarging jig. It was therefore necessary to use a new diameter-enlarging jig whenever a connection portion was formed. Accordingly, not only the diameter-enlarging jig was relatively expensive but also a great deal of time was required. Furthermore, in order to enlarge the inner diameter of the rubber insulator unit to about 200 %, an insertion force of about 1000 kgf and a draw-out force of about 1000 kgf were required for insertion and drawing-out of the diameter-enlarging jig. To solve the aforementioned problem, there has been proposed a method in which a diameter-enlarging jig is formed from a strong material to withstand the aforementioned insertion force and draw-out force or a diameter-enlarging jig which is split into pieces at its longitudinal center portion and in a direction perpendicular to its axis is used so as to be drawn out to opposite sides to thereby reduce the draw-out force. There has been also proposed a method in which a groove is provided in advance in an end surface of a diameter-enlarging jig taking the draw-out work into consideration, and a draw-out jig is fitted into the groove to draw the diameter-enlarging jig out easily. If the diameter-enlarging jig is split into pieces in a direction perpendicular to its axis, however, there is required a structure to withstand the insertion force at the time of insertion. [Means for Solving Problem] The present invention provides a jig for enlarging the diameter of a rubber insulator unit, in which the aforementioned problem is solved. The jig is characterized in that one pipe is split into pieces both in a direction perpendicular to the axis of the pipe and in a longitudinal direction of the pipe so that joints of the respective pieces obtained by splitting the pipe in the longitudinal direction are shifted from each other in a circumferential direction of the pipe. The jig is further characterized in that joint portions of the pipe split in the direction perpendicular to the axis of the pipe are connected to one another in the longitudinal direction of the pipe through engagement portions which are provided in the joint portions respectively. [Mode for Carrying Out the Invention] Fig. 1 is an external appearance view of an embodiment of the diameter-enlarging jig according to the present invention. One pipe constituting a diameter-enlarging jig is split into two pipe pieces 1 and 2 in a direction perpendicular to the axis of the pipe and substantially at the longitudinally center portion of the pipe. The pipe pieces 1 and 2 obtained by splitting the pipe as described above are further split into two pieces lA and IB and two pieces 2A and 2B respectively in a longitudinal direction of the pipe. A joint 4 of the aforementioned pieces lA and IB and a joint 5 of the aforementioned pieces 2 A and 2B are located so as to be shifted from each other in a circumferential direction of the pipe as shown in the drawing. Joint portions 3 of the pipe pieces 1 and 2 obtained by splitting the pipe in the direction perpendicular to the axis of the pipe as described above are connected to each other through engagement portions provided in the joint portions 3 as shown in the diagrams (A) and (B) of Fig. 2. That is, in the diagram (A) of Fig. 2, for example, a concave portion 3a is provided in one pipe piece 1 of the joint portions 3 and a convex portion 3b is provided in the other pipe piece 2 so that the concave portion 3 a and the convex portion 3b are fitted to each other to thereby connect the pipes pieces 1 and 2. Further, as another means, step portions 3C and 3d may be provided in the joint portions 3 of the pipe pieces 1 and 2 so that the step portions 3C and 3d are engaged with each other to thereby connect the pipe pieces 1 and 2. To correctly combine the piece lA with the piece IB in position to form the pipe piece 1, it is preferable that pins are formed on a circumferential end faces of the piece lA at the joint 4 whereas mating holes engageable with the respective pins are formed on a circumferential end faces of the piece IB at the joint 4. Fig. 4 only shows the pins 20 formed on the circumferential end faces of the piece lA at the joint 4. Similarly, it is preferable that pieces 2A and 2B are respectively provided with such pins and holes. To provide strength, it is preferable that each of the pipe pieces 1 and 2 is formed of metal. In addition, reference numerals Ic and 2c in Fig. 5 designate annular grooves formed on the pipe pieces 1 and 2, each of which is used to engage with a draw-out jig when the pipe piece 1 (2) is removed or drawn out from the rubber insulator unit 25. A process for fixing the rubber insulator unit 13 onto the connection portion of the electric power cable with the use of the jig of the present invention will be described hereafter. For simplify the explanation, the case where the step portions 3c and 3d are provided in the joint portions 3 of the pipe pieces 1 and 2 of the jig will be described. As shown in Fig. 5, the pieces 2A and 2B are combined together to form the pipe piece 2. Thereafter, the pieces lA and IB are combined together to form the pipe piece 1 in such a manner that the step portion 3c of the pipe piece 1 is located radially outside of the step portion 3d of the pipe piece 2 and engaged therewith and that the joint 4 of the pieces 1A and IB is shifted in a circumferential direction from the joint 5 of the pieces 2A and 2B. By mounting the pipe piece 1 onto the pipe piece 2 in this manner, the separation of the pieces 2A and 2B one from the other at the joint portion 5 can be surely prevented by the pipe piece 1. Further, a tapered tube 25 formed of metal, plastic or the like is mounted on the pip3 piece 1 such that the tapered tube is located radially outside the longitudinal end of the pipe piece 1. By mounting the tapered tube 25 onto the pipe piece 1 in this manner, the separation of the pipe pieces 1A and IB one from the other at the joint portion 4 can be surely prevented by the tapered tube 25. Further, the tapered tube 25 facilitates the insertion of the jig into the rubber insulator unit 13 while enlarging the diameter of the rubber insulator unit 13. The thus assembled jig constructed by the pipe pieces 1 and 2 and the tapered tube 25 is mounted on a compressor 30, and the rubber insulator unit 13 is also mounted on the compressor 30 such that the rubber insulator unit 13 is located longitudinally above the tapered tube 25, as shown in Fig. 6. The compressor 30 is designed such that the jig and the rubber insulator unit 13 can be mounted around a shaft portion 30A of the compressor 30, and a base portion 30B and a head portion 30C apply pressure onto the jig and the rubber insulator unit 13 in a longitudinal direction with the use of a hydraulic pump 30D. The pieces lA and IB of the pipe piece 1, the pieces 2 A and 2B of the pipe pieces 2 and the tapered tube 25 may be assembled together on and around the shaft 30A of the compressor 30. By activating the hydraulic pump 30D, the jig is forcibly inserted into the rubber insulator unit 13 while enlarging the diameter of the rubber insulator unit 13 as shown in Fig. 7. That is, the rubber insulator unit 13 can be mounted on the pipe pieces 1 and 2 of the jig. The pipe pieces 1 and 2 on which the rubber insulator unit 13 has been mounted is removed from the compressor 30 and the tapered tube 25 is also removed from the pipe piece 1. The pipe pieces 1 and 2 on which the rubber insulator unit 13 is mounted is loosely fitted on one of electric cables, and then the conductors of the electric cables are connected together to form the conductor connection portion 12 as shown in Fig. 8. Then, the pipe pieces 1 and 2 on which the rubber insulator unit 13 is moved so that the rubber insulator unit 13 is located around the conductor connection portion 12 and the insulated cores 11 as shown in Fig. 9. Then, the pipe piece 1 is removed (drawn out) from the rubber insulator unit 13 leftward, whereas the pipe piece 2 is removed (drawn out) from the rubber insulator unit 13 rightward as shown in Fig. 10, so that the rubber insulator unit 13 is mounted closely onto the insulated cores 11 by self-contracting force. Since the pipe piece 1 can be separated into the pieces lA and IB at the joint 4, whereas the pipe piece 2 can be separated into the pieces 2A and 2B at the joint 5, the pipe pipes 1 and 2 can be easily removed from the thus connected electric cables. [Effects of the Invention] As described above, in the diameter-enlarging jig according to the present invention, the joints of respective pieces obtained by splitting the pipe in the longitudinal direction of the pipe are shifted from each other in the circumferential direction of the pipe. Accordingly, no cut surface appears in the longitudinal direction of the pipe at the time of the insertion of the rubber unit. Accordingly, there is no occurrence of buckling, or the like, so that it is possible to obtain the same insertion force as that in the case of a single pipe. Further, the joint portions of the two pipe pieces obtained by splitting the pipe in the direction perpendicular to the axis of the pipe are coupled to each other through engagement portions. Accordingly, the pipe pieces are prevented from being disconnected from each other in the axial direction of the pipe, so that there is no risk of injuring the rubber insulator unit at the time of insertion. WE CLAIM : 1. A jig for enlarging the diameter of a rubber insulator, while mounting to a connection portion between two cables, said jig comprising a pipe split into pieces both in a direction perpendicular to the axis of said pipe and in a longitudinal direction of said pipe so that joints of the respective pieces obtained by splitting said pipe in said longitudinal direction are shifted from each other in a circumferential direction of said pipe. 2. The jig as claimed in claim 1, wherein joint portions of said pipe split in said direction perpendicular to the axis of said pipe are connected to one another in said longitudinal direction of said pipe through engagement portions which are provided in said joint portions respectively. 3. The jig as claimed in claim 1, wherein said pipe has a tapered end portion, a first pipe piece split into two semi-cylindrical pieces at a joint along a longitudinal direction, said first pipe having first and second longitudinal end portions, said first longitudinal end portion of said first pipe being connected to said end portion of said tapered end portion so that said tapered end portion prevents separation of said semi-cylindrical pieces of said first pipe piece; and a second pipe piece split into two semi-cylindrical pieces at a joint along the longitudinal direction, said second pipe piece having first and second longitudinal end portions, said first longitudinal end portion of the second pipe piece is mounted on the second longitudinal end portion of the first pipe piece so that said first pipe piece prevents separation of the semi-cylindrical pieces of the second pipe piece. 4. The jig as claimed in claim 3, wherein said tapered end portion is located radially outside of first longitudinal end portion of the first pipe piece. 5. The jig as claimed in claims 3 or 4, wherein said second longitudinal end portion of said first pipe piece has a step portion, said first longitudinal end portion of the second pipe piece has a step portion, and said step portion of said first pipe piece is located radially outside of said step portion of said second pipe piece. 6. The jig as claimed in claims 3 or 4, wherein said second longitudinal end portion of said first pipe piece has a concave portion, and said first longitudinal end portion of the second pipe piece has a convex portion engaged with said concave portion. 7. A jig for enlarging the diameter of a rubber insulator, substantially as hereinabove described and illustrated with reference to the accompanying drawings.

Documents:

2542-mas-1997 abstract duplicate.pdf

2542-mas-1997 abstract.pdf

2542-mas-1997 claims duplicate.pdf

2542-mas-1997 claims.pdf

2542-mas-1997 correspondence others.pdf

2542-mas-1997 correspondence po.pdf

2542-mas-1997 description (complete) duplicate.pdf

2542-mas-1997 description (complete).pdf

2542-mas-1997 drawings duplicate.pdf

2542-mas-1997 drawings.pdf

2542-mas-1997 form-19.pdf

2542-mas-1997 form-2.pdf

2542-mas-1997 form-26.pdf

2542-mas-1997 form-4.pdf

2542-mas-1997 form-6.pdf

2542-mas-1997 others.pdf

2542-mas-1997 petition.pdf