GB1569656A - Mould for sealing cables to submarine repeater housings - Google Patents

Description

(54) MOULD FOR SEALING CABLES TO SUBMARINE REPEATER HOUSING (71) We, STANDARD TELEPHONES AND CABLES LIMITED, a British Company, of 190 Strand, London, W.C.2, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to housings for telephone or telegraph repeaters and in particular to the provision of bulkhead glands in such housings.

An important feature of a telephone or telegraph repeater, and particularly a submarine repeater, is the construction of the bulkhead glands through which the cables feeding the repeaters are hermetically sealed.

The glands are generally injection moulded from a thermoplastics material such as polyethylene or polypropylene using a side gate mould. A major problem with such a construction is the critical control of the injection moulding process so that the ad vancing melt front spreads out across the mould so as to reach the various extremi ties substantially simultaneously. If this pro cess is not performed accurately- there is a considerable risk that two advancing melt fronts will meet to form a weld line with possible impairment of the - electrical and mechanical properties of the gland. Further more, injection of molten plastics via a side gate tends to cause deflection of the cable core. Tensioning of the centre conductor of the cable is required to reduce this effect.

According to the invention there is provided a ring gate mould assembly for pro viding an injection moulded plastics seal between a housing and a cable entering the housing, the assembly including a two part split mould having an axial bore for receiv ing and locating the cable, means for secur ing the mould to the housing, a side entry port for the injection of plastics material into the mould, and a ring gate insert located in a recess in the mould adjacent the entry port, arranged so as to obstruct the flow of plastics material injected from the entry port so as to deflect the plastics into a single melt front, said ring gate insert having an axial bore aligned with that in the mould and extending throughout the insert, and in which said ring gate insert has a cylindrical body portion whereby the in sert is located in a recess in the mould, and a smaller diameter ring portion extend ing from one end face of the insert and arranged eccentrically with respect to the axis of the body portion, and in which the insert is arranged with the eccentric ring portion adjacent the entry port.

An embodiment of the invention will now be described with reference to the accom panying drawings in which: Fig. 1 shows one half of a ring gate split mould for preparing an injection moulded plastics bulkhead gland; Fig. 2 shows the construction of the insert providing the ring runner and ring gate of the mould of Fig. 1.

Referring to the drawings, the mould is split into two halves one of which is shown in Fig. 1. The mould includes an elongated tail portion 11, a forward body portion 12 and a flange member 13 whereby the mould is secured to the housing of a repeater by bolts 14 during the gland moulding process.

The tail - portion 11 has an axial parallel bore 15 for receiving and securing a plastics coated cable (not shown) for connection to the repeater. A tube 16 communicating with the body portion 12, bore 15 and and mould cavity 22 is provided through the side of the mould for the injection of molten plastics material, e.g. polyethylene or polypropylene.

The mould is provided with heaters (not shown) to facilitate plastics injection and subsequent annealing.

The mould insert 31, (Fig. 2) which is made from the same material as the mould, comprises a cylindrical body portion 18 which locates in a corresponding recess 21 provided in the mould and has an axial bore 19 which, when the insert 31 is located in the mould, provides a continuation of the mould cavity 22. The ring runner of the insert 31 is provided by an eccentrically turned member 17 on the face of the insert adjacent the entry point of the injection tube 16.

The ring gate of the arrangement is provided by the predetermined clearance 23 between the recess 21 and the end face of the eccentric member 17. The insert 31 is located in the mould as shown in Fig. 1 such that. during the injection process, the molten plastics material fed through the tube 16 flows around the periphery of the ring runner 17 thus providing a radial flow of plastics material through the ring gate 23 and into the mould cavity 22.

To ensure a symmetrical flow of molten plastics into the mould. it is essential that the ring gate 23 presents the maximum impedance to the flow at the entry point of the injection tube 16. The mould insert 31 should therefore be arranged in the mould such that the eccentric ring runner 17 is disposed adjacent the injection tube 16. For this purpose the insert 31 is provided with one or more radial bores 24 for engaging a corresponding locating peg or pegs (not shown) in the mould cavity 21.

To prepare a bulkhead gland sealing a cable to a repeater housing, the insert 31 is threaded over the cable with the ring runner 17 facing away from the repeater. The two halves of the split mould are clamped together around the cable locating the insert in the recess and the ring runner 17 adjacent the injection tube 16. The mould assembly is secured to the repeater body via bolts 14 and molten plastics is injected through the tube 16. The injected plastics flows symmetrically into the mould displacing the original cable coating within the mould setting up a weld line interface between these two materials. To produce an effective weld it is important that the in jected plastics should be compatibIe with the cable coating. FLuallyt after annealing, the mould is removed to leave the completed gland seal.

WHAT WE CLAIM IS: 1. A ring gate mould assembly for providing an injection moulded plastics seal between a housing and a cable entering the housing, the assembly including a two part split mould having an axial bore for receiving and locating the cable, means for securing the mould to the housing, a side entry port for the injection of plastics material into the mould, and a ring gate insert located in a recess in the mould adjacent the entry port, arranged so as to obstruct the flow of plastics material injected from the entry port so as to deflect the plastics into a single melt front, said ring gate insert having an axial bore aligned with that in the mould and extending throughout the insert, and in which said ring gate insert has a cylindrical body portion whereby the insert is located in a recess in the mould.

and a smaller diameter ring portion extending from one end face of the insert and arranged eccentrically with respect to the axis of the body portion, and in which the insert is arranged with the eccentric ring portion adjacent the entry port.

2. A ring gate assembly as claimed in claim 1, and in which the insert has locating means for engaging corresponding locating means in the mould.

3. A ring gate mould assembly substantially as described herein with reference to the accompanying drawings.

4. A method of providing a bulkhead gland seal between a telephone or telegraph repeater and a cable feeding the repeater, which method is substantially as described herein with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. insert 31 is provided by an eccentrically turned member 17 on the face of the insert adjacent the entry point of the injection tube 16. The ring gate of the arrangement is provided by the predetermined clearance 23 between the recess 21 and the end face of the eccentric member 17. The insert 31 is located in the mould as shown in Fig. 1 such that. during the injection process, the molten plastics material fed through the tube 16 flows around the periphery of the ring runner 17 thus providing a radial flow of plastics material through the ring gate 23 and into the mould cavity 22. To ensure a symmetrical flow of molten plastics into the mould. it is essential that the ring gate 23 presents the maximum impedance to the flow at the entry point of the injection tube 16. The mould insert 31 should therefore be arranged in the mould such that the eccentric ring runner 17 is disposed adjacent the injection tube 16. For this purpose the insert 31 is provided with one or more radial bores 24 for engaging a corresponding locating peg or pegs (not shown) in the mould cavity 21. To prepare a bulkhead gland sealing a cable to a repeater housing, the insert 31 is threaded over the cable with the ring runner 17 facing away from the repeater. The two halves of the split mould are clamped together around the cable locating the insert in the recess and the ring runner 17 adjacent the injection tube 16. The mould assembly is secured to the repeater body via bolts 14 and molten plastics is injected through the tube 16. The injected plastics flows symmetrically into the mould displacing the original cable coating within the mould setting up a weld line interface between these two materials. To produce an effective weld it is important that the in jected plastics should be compatibIe with the cable coating. FLuallyt after annealing, the mould is removed to leave the completed gland seal. WHAT WE CLAIM IS:

1. A ring gate mould assembly for providing an injection moulded plastics seal between a housing and a cable entering the housing, the assembly including a two part split mould having an axial bore for receiving and locating the cable, means for securing the mould to the housing, a side entry port for the injection of plastics material into the mould, and a ring gate insert located in a recess in the mould adjacent the entry port, arranged so as to obstruct the flow of plastics material injected from the entry port so as to deflect the plastics into a single melt front, said ring gate insert having an axial bore aligned with that in the mould and extending throughout the insert, and in which said ring gate insert has a cylindrical body portion whereby the insert is located in a recess in the mould.

and a smaller diameter ring portion extending from one end face of the insert and arranged eccentrically with respect to the axis of the body portion, and in which the insert is arranged with the eccentric ring portion adjacent the entry port.

2. A ring gate assembly as claimed in claim 1, and in which the insert has locating means for engaging corresponding locating means in the mould.

3. A ring gate mould assembly substantially as described herein with reference to the accompanying drawings.

4. A method of providing a bulkhead gland seal between a telephone or telegraph repeater and a cable feeding the repeater, which method is substantially as described herein with reference to the accompanying drawings.