GB1584564A

GB1584564A - Machines for producing coaxial pairs

Info

Publication number: GB1584564A
Application number: GB3053077A
Authority: GB
Original assignee: Lignes Telegraphiques et Telephoniques LTT SA
Current assignee: Lignes Telegraphiques et Telephoniques LTT SA
Priority date: 1976-08-10
Filing date: 1977-07-20
Publication date: 1981-02-11
Also published as: CH620311A5; DE2735773C3; FR2361728B2; DE2735773B2; DE2735773A1; FR2361728A2

Abstract

The device comprises two half-cavities each defined by a stack of three small plates (inserts) (21-23), one (23) of which defines the radius and the thickness of the disk to be injection moulded. This small plate (insert) (23) is identical in all the half-moulds, as is one (21) of the lateral small plates (inserts), the other (22) being machined individually for the groove in which the stack occurs, of which this groove forms part, so that this stack exactly fills the groove which is assigned to it. <IMAGE>

Description

(54) IMPROVEMENT IN MACHINES FOR PRODUCING COAXIAL PAIRS (71) We, LIGNES TELEGRAPHI QUES ET TELEPHONIQUES - 89 Rue de la Faisanderie - 75782 PARIS CEDEX 16 FRANCE - a Body Corporate organized according to the laws of France, 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: The present invention relates to a machine for continuously moulding spacers on the inner conductor of a coaxial structure.

We have disclosed in the Specification of British Patent No. 629,625 an apparatus by means of which it is possible to use an injection moulding machine for continuously applying disc spacers to electric conductors which are continuously advanced through the apparatus. The Specification also discloses a machine in which endless chains carry portions of movable moulds which are joined together at the nozzle of the extrusion machine so as to bound the cavity through which the conductor passes and which defines the spacer to be moulded.

In the Specification of our French Patent No. 2,108,142 there is disclosed an improvement in machines for moulding, around a conductor, spacing elements necessary for centering the said conductor when the latter constitutes the inner conductor of a coaxial pair, more particularly intended to eliminate the periodic irregularities which said elements can present along the cable. The requirements imposed on coaxial pairs which are intended to transmit a wide spectrum of frequencies are very difficult to achieve in practice. An increase in the bandwidth to be transmitted at the upper end of the range is expressed, from the standpoint of technology, in an increase in the precision (dimensions and weight) of the constituent elements of the cable and more particularly of the spacing and centering elements.The referred to French Patent discloses a means of reducing the periodic irregularities by using chains with different numbers of mould portions.

The present invention provides a means of reducing the dispersion of the characteristics of the spacing elements in the case of continuous moulding machines for discs and of reducing the dimensions of the latter whilst maintaining the same precision. It has already been proposed in the Specification of French Patent No. 1,527,789 to machine the moulds with greater accuracy.

According to the present invention there is provided a machine for continuously moulding spacers on the inner conductor of a coaxial structure, in which the spacers are continuously sequentially moulded along an inner conductor by injection into sequential cavities, the inner conductor being continuously pulled through the machine, each cavity being defined between opposite mould halves which are each carried by one of a pair of opposed endless chains for continuous movement in cavity definining relationship past a location at which the injection is effected, wherein said mould halves each consist of a body equipped with a groove filled with a stack of at least two plates of which one is machines with a cavity corresponding to one half of the disc.

The use of mould portions of which the cavity is bounded by a stack of plates in a groove of a massive body makes it possible to use current machining methods whilst ensuring a precision which can increase the precision on the thickness of the disc by a factor of 10. This increase in precision is not found altogether in the volume of the discs, due to other causes of error (for example the precision on cutting off the moulding pin) but it is expressed as a reduction by one half of the maximum deviation in weight between discs produced by one and the same moulding line using the moulds of the prior art and those of the invention, which is expressed as a substantial improvement in the frequency response curve of the coaxial cable thus produced.

The present invention will now be described in greater detail by way of example with reference to the accompanying drawing, wherein: Figure I is an elevation view of one preferred form of female half mould; Figure 2 shows perspective views of the plates; Figure 3 is a plan view of the half mould shown in Figure 1; Figure 4 is a graph illustrating the two weight distributions of discs moulded by means of the same structure equipped with prior art moulds and with moulds made by machines constructed in accordance with the present invention.

Referring first to Figure 1, the female half-mould comprises a body 11 which is associated with a chain link 5. The body 11 is provided with a central groove 20 defining a housing into which the plates illustrated in Figure 2 will be introduced. The groove 20 is considerably larger than the imprint of a half-disc. The groove 20 is milled and ground, to a tolerance as high as 10-5m without special care.

Referring now to Figure 2, three plates 21, 23 and 22 respectively, are located in the groove 20 as will be seen from the plan view of the half mould shown in Figure 3. The central plate 23 is provided with a semicylindrical cavity 17 which define the thickness and the radius of the disc to be moulded by injection through a channel, one part of which is illustrated at 24, the complete channel being defined by a symmetrica wall carried by the plate located in the male half-mould (not shown) which cooperates with the female half-mould of Figure 1. The plates 21 and 22 located on each side of the central plate 23 define the lateral faces of the discs. A notch 25 located in each of the two other plates permits the passage of the central conductor. The central plates 23 associated with each of the half-moulds are identical.One of the side plates 21 is identical for all the half-moulds of the moulding chains, but on the other hand, the other side plate 22 is machined for each groove 20 so as to ensure the exact filling of the groove 20 without play. The three plates are machined then subjected to a smooth finish by polising until a surface state defined by SF N5 on the Rugotest scale is obtained.

Figure 3 is a plan view of the assembled half-mould showing the body 11, the three plates 21, 23, 22, the chain link 5, the housing 15 of the centering stud of the male half-mould, the cavity 17 defining the halfdiscs to be moulded and the channel 26 which, in coincidence with the notches 25, defines the passage of the inner conductor around which the discs are moulded.

The number of plates may be reduced to two (plates 22 and 23) if the machining of the groove 20 produces a surface state of the body 11 of sufficient quality to permit one of the lateral faces of the groove to be used for delimiting the disc. Moreover, the number of plates may be greater than three. The thickness of the moulded part as defined by the plate 23 is made as equal as possible for all the half-moulds constituting a moulding line.

Figure 4 illustrates the distribution of the weights of the discs obtained by means of a moulding line, the half-moulds of which are machined directly in the body (a prior art construction being shown by the thin line 30) and the distribution obtained by means of the same line after reworking the halfmoulds by machining a groove and constructing a mould by means of the three plates 21 to 23 (as shown the thick line curve 31). The ordinates represent the number of discs having a given mass (+ 0.1 mg) as a percentage of the total number of discs corresponding to a period of operation of the moulding line. The abscissae represent the weight, m being the nominal value and each division covering 0.2 mg, and being approximately 250 mg in the example which was used for the measurements plotted in Figure 4. It will be seen that the curve 30 has a much wider spread than the curve 31.All the discs are included in the interval m - 0.8 to m + 0.8 in the case of the above described example whereas the distribution of the discs according to the prior art occupies the interval m - 1.6 to m + 2.2, the weight deviations being expressed in milligrammes.

WHAT WE CLAIM IS: 1. A machine for continuously moulding spacers on the inner conductor of a coaxial structure, in which the spacers are continuously sequentially moulded along an inner conductor by injection into sequential cavities, the inner conductor being continuously pulled through the machine, each cavity being defined between opposite mould halves which are each carried by one of a pair of opposed endless chains for continuous movement in cavity defining relationship past a location at which the injection is effected, wherein said mould halves each consist of a body equipped with a groove filled with a stack of at least two plates of which one is machined with a cavity corresponding to one half of the disc.

2. A machine according to Claim 1, wherein said stack comprises three plates, one of which is of identical dimensions for all the half-moulds, and a second one which

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. same moulding line using the moulds of the prior art and those of the invention, which is expressed as a substantial improvement in the frequency response curve of the coaxial cable thus produced. The present invention will now be described in greater detail by way of example with reference to the accompanying drawing, wherein: Figure I is an elevation view of one preferred form of female half mould; Figure 2 shows perspective views of the plates; Figure 3 is a plan view of the half mould shown in Figure 1; Figure 4 is a graph illustrating the two weight distributions of discs moulded by means of the same structure equipped with prior art moulds and with moulds made by machines constructed in accordance with the present invention. Referring first to Figure 1, the female half-mould comprises a body 11 which is associated with a chain link 5. The body 11 is provided with a central groove 20 defining a housing into which the plates illustrated in Figure 2 will be introduced. The groove 20 is considerably larger than the imprint of a half-disc. The groove 20 is milled and ground, to a tolerance as high as 10-5m without special care. Referring now to Figure 2, three plates 21, 23 and 22 respectively, are located in the groove 20 as will be seen from the plan view of the half mould shown in Figure 3. The central plate 23 is provided with a semicylindrical cavity 17 which define the thickness and the radius of the disc to be moulded by injection through a channel, one part of which is illustrated at 24, the complete channel being defined by a symmetrica wall carried by the plate located in the male half-mould (not shown) which cooperates with the female half-mould of Figure 1. The plates 21 and 22 located on each side of the central plate 23 define the lateral faces of the discs. A notch 25 located in each of the two other plates permits the passage of the central conductor. The central plates 23 associated with each of the half-moulds are identical.One of the side plates 21 is identical for all the half-moulds of the moulding chains, but on the other hand, the other side plate 22 is machined for each groove 20 so as to ensure the exact filling of the groove 20 without play. The three plates are machined then subjected to a smooth finish by polising until a surface state defined by SF N5 on the Rugotest scale is obtained. Figure 3 is a plan view of the assembled half-mould showing the body 11, the three plates 21, 23, 22, the chain link 5, the housing 15 of the centering stud of the male half-mould, the cavity 17 defining the halfdiscs to be moulded and the channel 26 which, in coincidence with the notches 25, defines the passage of the inner conductor around which the discs are moulded. The number of plates may be reduced to two (plates 22 and 23) if the machining of the groove 20 produces a surface state of the body 11 of sufficient quality to permit one of the lateral faces of the groove to be used for delimiting the disc. Moreover, the number of plates may be greater than three. The thickness of the moulded part as defined by the plate 23 is made as equal as possible for all the half-moulds constituting a moulding line. Figure 4 illustrates the distribution of the weights of the discs obtained by means of a moulding line, the half-moulds of which are machined directly in the body (a prior art construction being shown by the thin line 30) and the distribution obtained by means of the same line after reworking the halfmoulds by machining a groove and constructing a mould by means of the three plates 21 to 23 (as shown the thick line curve 31). The ordinates represent the number of discs having a given mass (+ 0.1 mg) as a percentage of the total number of discs corresponding to a period of operation of the moulding line. The abscissae represent the weight, m being the nominal value and each division covering 0.2 mg, and being approximately 250 mg in the example which was used for the measurements plotted in Figure 4. It will be seen that the curve 30 has a much wider spread than the curve 31.All the discs are included in the interval m - 0.8 to m + 0.8 in the case of the above described example whereas the distribution of the discs according to the prior art occupies the interval m - 1.6 to m + 2.2, the weight deviations being expressed in milligrammes. WHAT WE CLAIM IS:

1. A machine for continuously moulding spacers on the inner conductor of a coaxial structure, in which the spacers are continuously sequentially moulded along an inner conductor by injection into sequential cavities, the inner conductor being continuously pulled through the machine, each cavity being defined between opposite mould halves which are each carried by one of a pair of opposed endless chains for continuous movement in cavity defining relationship past a location at which the injection is effected, wherein said mould halves each consist of a body equipped with a groove filled with a stack of at least two plates of which one is machined with a cavity corresponding to one half of the disc.

is identical for all the half-moulds and bears the half cavity.

3. A machine according to Claim 1, wherein the stack comprises two plates, of which one which is identical for all the half-moulds and bears the half-cavity, and the second of which is machined to completely fill each groove without play.

4. A machine for continuously moulding spacers on the inner conductor of a coaxial structure substantially as herein described with reference to and as illustrated in the accompanying drawings.